How to cook
Preheat oven to 356°F (180 °C) and grease and flour 2 forms with peel-off sides with a diameter of 26 cm, you can use one as the bases must bake one after another. With a mixer, beat the butter and sugar into a smooth and fluffy cream.
Add the vanilla and eggs one at a time while continuously beating. Gradually add the flour mixture, baking powder and salt. Pour milk and beat again. Bake the mixture into 2 bases, each for about 30 minutes or until a checking toothpick comes out dry. Remove the ready form and leave to cool on a wire rack for 5 minutes.
In a pot, on the stove, heat the cream over low heat. Once small bubbles form, stir in the sugar until dissolved and set aside to be cooled. Separately, dissolve the cornstarch in milk, then add the eggs, beating with a mixer. To egg mixture, add 2-3 tablespoons of the hot cream to temper it. Then gradually pour in the egg mixture constantly whipping the cream.
Put the dish back on the stove over low heat and stir constantly for about 5 minutes - until thickened. Remove from the heat and add vanilla and rum. Cover the container with clear film and leave it to cool.
For the icing, mix all ingredients in a saucepan on the stove and stir until everything is melted and homogenized. Remove and stir until cooled slightly. In a suitable tray, assemble the two cake bases and add glaze.
Allow icing to soak slightly into the walls of your Boston cream pie. Leave to stand for 2-3 hours before you serve.