Boston Cream Pie gets a keto makeover! I recently updated this low carb recipe and now it’s even better than before, with fewer carbs. Tender almond flour cake filled with sugar free vanilla pastry cream and a rich low carb chocolate glaze.
I lived in the Boston area for over 11 years and the first time I ever tried this classic cake was when I made my own low carb version, way back in October of 2011. Given that it’s the city’s official dessert (according to the ever reliable Wikipedia), it’s quite astonishing that I never gave this delicious dessert the time of day. Don’t make the same mistake I did, my friends! Make this Boston Cream Pie recipe as soon as you can and you will be ever so glad you did.
Is it a pie or a cake?
If you’ve ever been to Boston, you will know just how confusing that city it, with its meandering avenues and lack of good street signs. Possibly you even asked someone for directions and got quite turned around, trying to make sense of their multi-step instructions. Believe me when I say that driving around that town is not for the faint of heart. Any of you who have ever driven on Storrow Drive know exactly what I am talking about!
Well, in keeping with the Bostonian way of making things confusing, Boston Cream Pie isn’t a pie at all, but really a cake. A cake filled with vanilla pastry cream and topped with chocolate. Okay, so it may seem like they are deliberately trying to confound outsiders with improper names and poor street signage, but when it comes to dessert, Bostonians aren’t messing around! You can’t really go wrong with a custard-filled cake topped with luscious chocolate ganache. Now that I’ve made my own and tasted it, it’s quite shocking I never did it before.
Updated Boston Cream Pie Recipe
My original low carb recipe was at the request of a reader, wayyyyyyy back in 2011. Boy that seems like a long long time ago! Even back then, I was pretty deft at low carb baking and it was relatively easy to figure out how to make over this classic cake and reduce the sugar and carbs. But over the past 7 years, I have honed my keto baking skills , so it was time to tackle a little update.
For one thing, the cornstarch in the vanilla pastry cream had to go. That is not something I use at all anymore and I’ve found that xanthan gum or glucomannan work much better as a keto thickener. I also added an extra egg yolk to help thicken the cream filling.
But I still found it a bit on the goopy side so I whisked in just a touch of coconut flour so that it didn’t ooze out too much between my cake layers. You may find you don’t need it, depending on how well your pastry cream thickens up.
I reduced the carbs in the cake layers as well, by using my standard vanilla cake recipe but by subbing out one of the cups of almond flour for a 1/3 cup of coconut flour.
Next up I tackled the glaze. I used to make a chocolate glaze that was based in butter but I’ve found that I can actually make a really good keto chocolate ganache the traditional way, by simmering cream and then melting the chocolate in the cream. Of course I can’t use chocolate with sugar, so I use unsweetened chocolate and whisk in a little sweetener at the end.
The thickness of your chocolate glaze will depend a little on the brand of cocoa powder you use (I used Rodelle). This is why I’ve also added instructions for thinning or thickening the glaze as necessary.
The Results
The truth is that the updated Boston Cream Pie recipe and the old version are both really good and they taste about the same. They both have a creamy center and a rich chocolate glaze. And oh, is there anything prettier than chocolate ganache dripping down the sides of a cake? I think not! But this new recipe is simpler and more straightforward. And it skips the icky ingredients like cornstarch, so you know this will fit in well with your keto diet.
I took this to a friend’s house for an end-of-summer barbecue and it was devoured by everyone! You know it’s good when even the non-low carbers give it rave reviews.
Looking for more delicious keto cake recipes? Check out my page of Keto Desserts here!
Low Carb Boston Cream Pie
Ingredients
Pastry Cream: (make this first and let it chill while making the other parts)
- 1 1/4 cups heavy whipping cream
- 4 egg yolks
- 6 tbsp powdered Swerve Sweetener
- pinch salt
- 2 tbsp butter cut into two pieces
- 1 1/2 tsp vanilla extract
- 1/2 tsp xanthan gum
- 2 tsp coconut flour, sifted (only if you need it!)
Cake:
- 2 cups almond flour (about 210g)
- 3/4 cup Swerve Sweetener
- 1/4 cup coconut flour
- 1/4 cup unflavored whey protein powder
- 2 tsp baking powder
- 1/4 tsp salt
- 3 large eggs
- 1/2 cup butter melted
- 1/2 tsp vanilla extract
- 1/2 cup water
Chocolate Glaze:
- 2/3 cup heavy whipping cream
- 2 oz unsweetened chocolate chopped
- 1/4 cup powdered Swerve Sweetener
- 1 tbsp cocoa powder
- 1/2 tsp vanilla extract
Instructions
Pastry Cream
- Bring the whipping cream to a simmer in a medium saucepan over medium heat. In a medium bowl, whisk the egg yolks with the sweetener and salt until well combined.
- Slowly whisk about half of the hot cream into the yolks to temper, then slowly return the yolk/cream mixture back to the saucepan and cook until thickened, about 4 to 5 minutes, whisking continuously. It thickens up very suddenly and quickly, so watch it carefully!
- Remove from heat and whisk in the butter and vanilla extract. Sprinkle the surface with xanthan gum, whisking as you go, to combine well. Let cool to room temperature and then refrigerate at least 3 hours.
Cake
- For the cake, preheat the oven to 350F. Grease 2 (two) 8-inch round cake pans and line with parchment paper. Then grease the paper as well.
- In a medium bowl, whisk together the almond flour, sweetener, coconut flour, protein powder, baking powder, and salt, breaking up any clumps with the back of a fork.
- Stir in the eggs, melted butter, and vanilla extract until well combined. Stir in just enough water so that the batter is spreadable but not pourable. Divide the batter evenly between the prepared baking pans and spread to the edges.
- Bake 20 to 25 minutes minutes or until edges are golden brown and the top is just firm to the touch. Cool in the pan 10 minutes and then flip out onto a wire rack to cool completely.
Chocolate Ganache
- In a small saucepan over medium heat, bring the whipping cream to a simmer. Remove from heat and add the chopped chocolate. Let sit 3 to 4 minutes to melt.
- Add the powdered sweetener, cocoa powder, and vanilla and whisk until smooth. Let cool 5 to 10 minutes, while assembling cake, until the glaze is thicker but still pourable. If it's too thick, gently re-warm with an additional tablespoon or two of cream. If it's too thin, whisk in another tablespoon of cocoa powder until smooth.
To Assemble
- Whisk the chilled pastry cream briskly to remove any clumps. If you find it's very gooey and likely to ooze out between the layers of cake, whisk in a bit of sifted coconut flour to help thicken it.
- Place one layer of cake on serving dish and spread with the pastry cream. Gently top with the second layer. Pour the chocolate glaze over the top of the cake and spread with a knife or offset spatula, pushing to the edges and letting it drip down over the sides.
- Pour the chocolate glaze over the top of the cake and spread with a knife or offset spatula, pushing to the edges and letting it drip down over the sides. Refrigerate the cake 1 hour before serving.
The old low carb Boston Cream Pie. Looks pretty good even for an old old recipe!
Donna Lewis says
Hello Caroline: first, let me say how much I enjoy reading and trying out your recipes. I have been looking for a Boston cream pie/ cake for a while and came across yours. My question is, would it be acceptable to use whey protein isolate instead of whey protein powder? That’s about all I have right now and I really want to make this. Thanks for answering.
Carolyn says
Yes, that works just fine.
Mark says
Hi Carolyn. I plan to make this next weekend. Can I make the pastry cream the day before I make the rest of the cake? Will the pastry cream keep ok a day in advance chilled? Thank you!
Carolyn says
Yes, it should be fine. Press plastic wrap on the surface before refrigerating so that it doesn’t develop too much of a skin.
Mark says
Thank you! I love your website and have made several of your dessert recipes. They’ve all been excellent! Thank you for providing such a valuable service!
Carolyn says
You are most welcome!
Emily says
Sorry if I missed the answer to my question in your blog post. Does this cake freeze well? I’m looking to make it about a week or so in advance from my littles birthday so that I can have time to focus on the cream and glaze without complete chaos in my itty bitty kitchen.
Carolyn says
To be honest, I would freeze without the chocolate glaze and do that on the day of.
RachelH (& Gary) says
Yesterday was our 5th Anniversary . . . over the years, he has mentioned that one time he asked for Boston Cream for his Birthday Cake, as it is his favorite cake.
So I *finally* made this. I made this cake, and it’s gone! I think we ate it 2x AnniDay, 3x today . . . I dunno, the last 2 days are a blur of “Snack Time, get the Pie”, and “This is my favorite cake, can you make it again next week?”
Thank you, Carolyn! Your recipes always please!
Gary thanks you, too!
Carolyn says
So great to hear!
Anastasia says
Love it! The cake couldn’t be more perfect – moist, fluffy, perfect custard filling and choc topping – everything turned out perfect. Made this for a party of 30 some people – I can’t believe how fast was GONE !! Thanks for the amazing blog – love all the recipes here !
Joie Steen says
Recipe looks good. All your recipes look good.
We can’t get Swerve in Australia. Would appreciate the provision of substitutes that we can swap for Swerve.
Carolyn says
I think Natvia is similar?
Sharon Everett says
Hi Carolyn, I made this for my husbands birthday…it is his most favorite dessert…and it was a hit! He loved it and I did too:) . I am not a great baker and this was way out of my comfort zone but I did an amazing job with your recipe and instructions. Really appreciate your website:) .
Carolyn says
Well happy birthday to him and I am glad you found the recipe helpful!
Fara says
Hi Carolyn, I was wondering if you have any recipe for pastry crea filled recipe? I really want to try your pastry cream with donuts. Thanks
Ruth Turner says
I just made this for my father’s 74th birthday and it was a hit! I took the precaution of shifting the almond flour before I made the cake and it helped to make it fluffy. I will definitely use this recipe again. Thank for for your hard work.
Carolyn says
That’s so lovely. Thank you!
Ashlea says
I just made this for the first time and lol I have to say it took me twice as long to make it lol! I’m very excited to try it, waiting it out for the hour so I don’t compromise any of the flavours.
Thank you for sharing this awesome recipe!!