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 ⅓ 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 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
Pastry Cream: (make this first and let it chill while making the other parts)
- 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.
- 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.
- 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.
- 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.