Keto Boston Cream Pie
Published June 16, 2026
This post may contain affiliate links. See my disclosure policy.
This Keto Boston Cream Pie has everything you love about the classic dessert: soft, moist vanilla cake layers, a light and fluffy custard filling, and a rich chocolate topping. Made with a special low carb flour blend, it's the kind of showstopping dessert nobody will believe is low carb.
I’ve never understood why they call it Boston Cream Pie when it’s clearly a cake. The first time I had one, I was expecting a pie and instead got layers of vanilla cake sandwiched around a creamy custard filling and topped with chocolate. Whatever the reason behind the name, I’ve been a fan ever since. I’m also a complete sucker for any dessert that combines cream filling and chocolate, so creating a keto Boston cream pie was high on my list.
The challenge with making a low carb version is getting the cake texture right. I didn’t want dry, dense cake layers that fall apart the second you slice into them. That’s why I use a special flour blend. The combination of almond flour and oat fiber creates a cake that’s soft, moist, and tender while still holding up to that thick layer of custard in the middle. Almond flour brings a great flavor and keeps the recipe approachable since it’s one of the easiest keto flours to find, while oat fiber helps create a texture that’s much closer to traditional cake.
And then there’s the custard filling, which might be my favorite part of the whole dessert. It’s rich, silky, and surprisingly fluffy, but getting that texture comes down to one important step during cooking. Once layered between the vanilla cake and finished with a rich chocolate topping, you end up with a dessert that looks impressive enough for a special occasion but tastes like something you’d happily sneak a slice of straight from the refrigerator. If you’ve been missing Boston cream pie since going low carb, this recipe delivers everything you remember about the classic version.
Explore hundreds of keto recipe videos with step-by-step instructions, tips, and tricks to make keto easy.
Vanilla Cake Ingredients
2 cups almond flour -
2/3 cup oat fiber
-
1/3 cup egg white protein powder
-
2 tablespoons baking powder
-
1 tablespoon xanthan gum
-
1 tablespoon arrowroot powder
-
1/2 teaspoon salt
-
1/2 cup unsalted butter, softened to room temperature
-
1/2 cup olive oil
-
1 ¾ cups granulated allulose sweetener
-
4 large eggs
-
2 teaspoons vanilla extract
-
1 ¼ cup milk of choice
Custard Filling Ingredients
-
6 large egg yolks
-
1 cup granulated allulose sweetener
-
1/4 cup cornstarch
-
pinch of salt
-
2 cups milk of choice
-
1/2 cup heavy cream
-
2 tablespoons unsalted butter, softened
-
2 teaspoon vanilla extract
Chocolate Frosting Ingredients
-
1 ⅓ cup powered allulose
-
3 tablespoons unsweetened cocoa powder
-
3 tablespoons hot water
-
1 teaspoon unsalted butter, softened
-
1 teaspoon vanilla extract
Equipment Ingredients
-
Two 8-inch round cake pans
-
parchment circles
Step by Step Instructions
Step by Step Instructions
Prepare the cake pans
Spray two 8-inch round cake pans with cooking oil and line the bottom with a parchment circle. Preheat the oven to 350 degrees F.
Special keto flour blend
In a medium bowl, sift together almond flour, oat fiber, egg white protein powder, baking powder, xanthan gum, arrowroot powder, and salt. Set the bowl aside.
- 2 cups almond flour
- 2/3 cup oat fiber
- 1/3 cup egg white protein powder
- 2 tablespoons baking powder
- 1 tablespoon xanthan gum
- 1 tablespoon arrowroot powder
- 1/2 teaspoon salt
Mix wet ingredients
In a large bowl, cream together 1/2 cup butter, oil and 1 ¾ cups granulated allulose using an electric mixer at medium speed. Mix until light and fluffy for about 3-4 minutes. Mix in eggs one at a time. Then mix in 2 teaspoons vanilla extract.
- 1/2 cup unsalted butter, softened to room temperature
- 1/2 cup olive oil
- 1 ¾ cups granulated allulose
- 4 large eggs
- 2 teaspoons vanilla extract
Finish cake batter
Using a spatula, pour in about ¼ of the milk to the butter mixture. Mix until combined. Then sprinkle in ¼ of the dry ingredients and mix until combined. Continue alternating between adding each and mixing until just combined.
- 1 ¼ cup milk of choice (I used macadamia nut milk)
Bake the cakes
Evenly divide the cake batter between the two prepared cake pans. Bake at 350 degrees F for 28-30 minutes or until a toothpick inserted into the middle comes out clean. Remove the pans from the oven and set aside to cool for 3-4 minutes. Loosen the sides of the cake with a knife and then flip onto a wire rack to cool completely.
Make the custard
In a medium saucepan, whisk together egg yolks and sugar until well combined. Whisk in cornstarch and salt. In a slow, steady stream, whisk in milk and then the cream. Add butter. Cook mixture over medium-low heat, stirring constantly with a wooden spoon, just until it starts to thicken. Immediately whisk mixture until smooth, then continue to cook and stir custard until it has come to a very low boil for 2 minutes, about 6 to 8 minutes total. Stir in vanilla. Cover with plastic wrap, pressing the plastic directly onto the surface. Chill for at least 3 hours and up to 24 hours.
- 6 large egg yolks
- 1 cup granulated allulose
- 1/4 cup cornstarch
- pinch of salt
- 2 cups milk of choice
- 1/2 cup heavy cream
- 2 tablespoons unsalted butter, softened
- 2 teaspoon vanilla extract
Make chocolate ganache
In a small bowl, combine powdered allulose and cocoa powder. Stir in hot water, butter and vanilla. Mix until combined. If frosting is too thick, add another ½ tablespoon of hot water until desired consistency is reached.
- 1 ⅓ cup powdered allulose
- 3 tablespoons unsweetened cocoa powder
- 3 tablespoons hot water
- 1 teaspoon unsalted butter, softened
- 1 teaspoon vanilla extract
Assemble
To assemble, pile on the custard filling to one cake layer and spread around evenly, then top with second layer. Add the chocolate frosting on top of the cake and either spread it to the edges or you can let it spill over a bit.
Nutrition disclaimer
The nutrition information provided is an estimate and is for informational purposes only. I am a Doctor of Pharmacy (Pharm.D.); however, this content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or other qualified health provider before making any lifestyle changes or beginning a new nutrition program.
Your Macros. Your Recipes. Calculated in 60 Seconds.
Get personalized keto macros and instantly see which recipes fit your targets. No more guessing what to eat.
Get My Macros + Recipes →Frequently Asked Questions
Can I make this ahead of time?
Yes! In fact, I think it tastes even better after a few hours in the refrigerator. The custard has time to fully set and the flavors meld together. You can make the entire cake up to 24 hours in advance and keep it covered in the refrigerator until ready to serve.
Why do I need to sift the dry ingredients?
Sifting helps break up clumps from the oat fiber, egg white protein powder, and almond flour, resulting in a smoother cake batter and more even texture. It's a small step that makes a noticeable difference in the finished cake.
Can I use coconut flour instead of the flour blend?
No. Coconut flour absorbs liquid very differently than almond flour and oat fiber, so it can't be substituted one-for-one in this recipe. For the best texture, stick with the flour blend as written.
Why is my custard runny?
A runny custard is usually caused by not cooking it long enough or not chilling it long enough. Make sure it reaches a low boil and cooks for 2 minutes, then chill it for at least 3 hours before assembling the cake.
