Make up to 5 days in advance and store in the refrigerator until assembly.
Preheat oven to 350F and position the rack to the lower third. Spray 2, 6-inch round cake pans with baking spray and cut a piece of parchment paper to fit into the bottom of each. I trace the bottom of the pans on a piece of parchment and cut inside the line.
Measure all of the Dry Ingredients into a medium bowl and whisk together. Add all of the Wet Ingredients into a smallish bowl and beat well.
Cream: In a large bowl, whip the butter until it is smooth and there are no lumps. Powder the eryhtritol and add to the butter. Whip with a hand mixer for 30 seconds to a minute on medium high to high speed until light, fluffy and cold. Scrape down the bowl. Add one egg and whip for another minute. Scrape down the bowl.
Combine: Add about 1/3 of the dry ingredients into the creamed butter and sugar mixture and mix until completely incorporated but still fluffy. Add half of the wet ingredients, mixing until completely and thoroughly mixed. Scrape down the bowl. Add half of the remaining dry ingredients, mixing until completely incorporated and then the rest of the wet ingredients, mixing until completely incorporated. Scrape down the bowl. Add the last of the dry ingredients mixing well. The batter should be very thick and mousse-like.
Prepare the Pans: Add half of the batter to each pan and spread the batter evenly with a small off-set spatula. Lift each pan a few inches above the counter and drop it about 3 times. This will knock out the big air bubbles.
Bake: Place the pans into the oven and raise the oven temperature to 400 for 5 minutes. Then turn it back down to 350 and bake 30-40 minutes or until a toothpick inserted into the middle comes out clean. Remove the pans to a cooling rack and cover them with a clean tea towel until they are completely cool. They will sink in the middle a little upon cooling. Cool completely before assembly. Can be made ahead and frozen then thawed or made several days before assembly and refrigerated.
Pour the heavy cream into a small bowl and add the vanilla and sweetener. Whip on high speed until soft peaks form. Sprinkle the pinch of xanthan gum over the top and whip. It should get very stiff and almost start to pull or clump together. If not add just a pinch more. It should be very thick, firm and mousse-like. Make the day of assembly.
Remove the Vanilla Pastry Cream from the fridge and whip it with a hand mixer until it is nice and light. Place 1/3 of the whipped cream into a pastry bag or zip-loc bag fitted with a large round tip. Carefully slice the cakes in half horizontally. Some people find it easier to use a piece of floss for this (make sure it isn't flat floss).
Place one cake half on your serving plate. Pipe a circle of whipped cream along the inside-edge of the cake. Place 1/3-1/2 cup of pastry cream onto the center of the cake and spread to the whipped cream with a small off-set spatula. Top with a layer of cake and create another dam of whipped cream and fill with more pastry cream. Repeat this process one more time, then top with the remaining cake layer. You will have pastry cream left over.
Squeeze the remaining whipped cream into the larger amount of whipped cream and starting with the sides ans using a larger off-set spatula, frost the cake with the whipped cream. I decorated the top of the cake with some of the extra pastry cream.
Refrigerate until ready to serve. Serves 12 at 7 net carbs per serving.
*I use cold eggs in all of my baking recipes because the erythritol makes things cold when melts into the batters anyway.
Low Carb Chocolate Birthday Cake
Amount Per Serving
Calories 398Calories from Fat 333
% Daily Value*
* Percent Daily Values are based on a 2000 calorie diet.