Creating your Boston Cream Pie Trifle is simple when you follow these steps:

1. Bake the Sponge Cake:
– Preheat your oven to 350°F (175°C). Grease and flour an 8-inch round cake pan.
– In a medium bowl, combine flour, baking powder, and salt. Set aside.
– In a large mixing bowl, beat the butter and sugar together until light and fluffy.
– Add eggs one at a time, mixing well after each addition. Stir in the vanilla.
– Gradually add the dry ingredients alternately with milk until just combined.
– Pour the batter into the prepared pan and bake for 20-25 minutes or until a toothpick inserted comes out clean.
– Cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

2. Prepare the Vanilla Custard:
– In a saucepan, combine the milk, sugar, cornstarch, and salt. Whisk until well mixed.
– Cook over medium heat, stirring constantly until the mixture thickens.
– Remove from heat, then whisk in egg yolks and cook for another 2 minutes.
– Stir in butter and vanilla extract, and set aside to cool.

3. Make the Chocolate Ganache:
– In a small saucepan, heat the heavy cream until hot but not boiling.
– Pour over the chocolate chips in a bowl. Let it sit for a few minutes, then stir until smooth. Allow to cool slightly.

4. Assemble the Trifle:
– Cut the cooled sponge cake into cubes or slices.
– In a trifle bowl or individual serving glasses, start layering by adding a layer of sponge cake.
– Follow this with a layer of vanilla custard, then a layer of chocolate ganache.
– Repeat layers until the bowl is filled and finish with a layer of whipped cream on top.
– Chill in the refrigerator for at least one hour before serving.