Slightly beat egg yolks in a medium bowl and set aside.
In a large saucepan, mix milk, cornstarch and sugar until smooth. Turn heat to medium and cook until thickened stirring continuously about 2 minutes. Remove from heat.
Add about 3 tablespoons of the milk mixture to the egg yolks and stir then add the whole egg mixture to the pan. Bring back to heat and bring to a slow boil while stirring continuously about 2 minutes.
Remove from heat and add butter and vanilla. Stir to incorporate then transfer to a glass bowl and place a cling wrap directly on top of the cream. Let cool completely in the fridge about 2 hours.
VANILLA CAKE:
Line 2 (9 inch) cake pans with parchment papers cut into circles. Rub butter around the sides and set side.
Preheat oven to 350 degrees F.
In a large bowl, combine all the dry ingredients and in a separate bowl combine all the other ingredients. Slowly mix them together and beat on medium speed until nice and smooth.
Divide the batter into the prepared pans. Bake from 23 to 25 minutes or until a toothpick inserted in the middle comes out clean. Remove from oven and let it cool completely. Use a serrated knife to even out the tops of the cakes if necessary.
Stir the pastry cream until smooth.
Place one of the cakes on a platter and top with the cream before placing the other cake on top. Pour and spread the chocolate ganache over cake. Let it drip on the sides. Refrigerate for a couple of hours before serving. Yum!
CHOCOLATE GANACHE:
Combine the chocolates and syrup in a medium bowl.
Heat the whipping cream in a small saucepan until it starts to boil. Pour the cream into the chocolates and let it sit for a minute before stirring until very smooth.
Recipe by The Gluten Free at https://www.theglutenfree.com/gluten-free-boston-cream-pie/