Creating the perfect Boston Cream Pie is easy when you follow these simple steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
2. Mix Dry Ingredients: In a mixing bowl, combine flour, baking powder, and salt. Set aside.
3. Cream Butter and Sugar: In another bowl, cream the softened butter and granulated sugar until light and fluffy.
4. Add Eggs and Vanilla: Beat in the eggs one at a time, followed by the vanilla extract.
5. Combine Mixtures: Gradually add the dry ingredient mixture to the butter mixture, alternating with milk. Stir until smooth.
6. Bake the Cake: Divide the batter evenly between the prepared pans and bake for 25-30 minutes. The cakes should be golden brown and a toothpick inserted in the center should come out clean.
7. Cool the Cakes: Allow the cakes to cool in the pans for 10 minutes, then transfer to wire racks to cool completely.
8. Prepare Custard Filling: In a saucepan, heat the milk over medium heat. In a separate bowl, whisk together sugar, egg yolks, and cornstarch. Gradually add the hot milk to the egg mixture, stirring constantly. Return to the saucepan and cook over low heat until thickened. Remove from heat and stir in butter and vanilla. Allow to cool.
9. Assemble the Cake: Place one cake layer on a serving plate. Spread the cooled custard filling evenly over the top. Place the second cake layer on top.
10. Make Chocolate Glaze: In a saucepan, heat the cream until just simmering. Pour it over the chopped chocolate and let sit for a few minutes, then stir until smooth. Add butter and mix until incorporated.
11. Top with Chocolate Glaze: Pour the chocolate glaze over the top of the assembled cake, allowing it to drip down the sides.
12. Chill: Refrigerate the cake for at least an hour to set the filling and glaze.

These steps will guide you in creating a delicious Boston Cream Pie that will impress everyone!