Preheat oven to 325F and grease an 11x17 inch rimmed sheet pan well.
In a medium bowl, whisk together almond flour, coconut flour, whey protein powder, baking powder, and salt.
In a large bowl, beat together the peanut butter and butter until well combined. Beat in sweetener, and then beat in eggs and vanilla extract.
Add half the almond flour mixture and beat until well combined and then beat in almond milk. Beat in remaining almond flour mixture until well combined.
Spread batter in prepared pan and smooth the top. Bake 18 to 22 minutes, until edges are golden brown and cake is set. Remove and let cool in pan.
In a large bowl, beat cream cheese, butter and peanut butter until well combined. Beat in sweetener, cream and vanilla extract until mixture is smooth.
Spread frosting evenly over cooled cake. Sprinkle with chopped peanuts.
Serves 20. Each serving has 7.14 g NET CARBS. (It's pretty rich so you can get more like 24 servings out of this, if you cut them a bit smaller).Food energy: 386kcal Total fat: 32.89g Calories from fat: 296 Cholesterol: 75mg Carbohydrate: 10.37g Total dietary fiber: 3.23g Protein: 11.35g