Preheat oven to 350°F and prepare a 9-inch springform pan by buttering and wrapping the outside with foil.
Sift together cake flour, baking powder, and salt.
Beat egg yolks with 1/3 cup sugar until light and fluffy, about 5 minutes, then add vanilla extract.
Fold the sifted flour mixture into the yolk mixture and blend in melted butter.
In a separate bowl, beat egg whites with cream of tartar until foamy; gradually add 2 tablespoons sugar until stiff peaks form.
Fold the egg whites gently into the batter and spread evenly in the prepared pan.
Bake the cake layer for 13-15 minutes until set; allow to cool completely.
Prepare the cheesecake layer by beating one package of cream cheese with 1/3 cup sugar and cornstarch until smooth.
Add the remaining cream cheese, then beat in remaining sugar and vanilla extract.
Add eggs one at a time, then mix in the heavy whipping cream.
Pour the cheesecake mixture over the cooled cake layer in the pan.
Place the pan in a water bath and bake for 75-85 minutes until the center just jiggles.
Cool cheesecake for 1 hour, then refrigerate for at least 4 hours or overnight.
To make the pastry cream, beat heavy cream, pudding mix, and milk on high speed until thickened.
Spread the pastry cream evenly over the chilled cheesecake.
Prepare the chocolate glaze by melting chocolate, corn syrup, and butter in the microwave, stirring until smooth.
Cool the glaze slightly, then pour evenly over the pastry cream layer.
Serve chilled and enjoy this rich Boston Cream Pie Cheesecake.