What dessert is called a pie, but is truly a cake? The answer is Boston Cream Pie which is actually a cake which had its layers baked in pie tins known as "Washington Pie Plates". This dessert was created by French Chef Sanzian to commemorate the opening of the Parker House Hotel in 1856. Now the dessert he created was more elaborate than what we typically see in Boston Cream Pie or Cake, both names are commonly interchanged, today.
Instead of pie plates, a 9 or 10 inch springform pan is used to bake the cake which is then divided into two layers. The Boston Cream Cake is not a dessert that can be made at the spur of the moment; there are four crucial steps. First the sponge cake, more dense and less crumbly than regular vanilla cake, needs to be mixed together and baked. Secondly is the pastry cream; a thick, rich pudding containing corn starch to help it hold up under the weight of the top layer of cake. Third, and oh so important, is the chocolate ganache; made from a cooked combination of chopped chocolate and heavy cream which cools quickly to make a rich, firm topping to the cake. Typically for the ganache, milk or semi-sweet chocolate is used, but I prefer Ghirardelli Bittersweet Chocolate. It melts quickly, the texture is smooth and the sheen is glossy; the bittersweet chocolate complements the pastry cream and sponge cake wonderfully. Step four is the construction of the cake, not too difficult and the results are worth waiting for.
Why this dessert cannot be a spur of the moment decision to make is that the cake and cream should be cool before the layering process begins; otherwise you'll be looking at one hot mess oozing off the plate. Now wait, let me correct myself a bit; this can be made spur of the moment by using a premade pound cake and instant pudding; might look pretty, but it won't taste the same as the authentic cake.
Boston Cream Pie (Cake)
Step One: The Sponge Cake
3 Tbsp melted butter, cooled to room temperature
6 large eggs
1 cup sugar
3 tsp pure vanilla extract
1 cup flour, sifted
1/4 tsp salt
Preheat oven to 350F. From parchment paper, cut a circle to line bottom of a 9 or 10 inch springform pan. Smear a little butter onto bottom and sides of pan first, sprinkle a light dusting of flour; put parchment paper circle on pan bottom and lightly smear butter on the paper.
In a large bowl, mix the melted butter and sugar together until fluffy and a yellow color. Add the extract and half the flour; mix for one minute before adding remaining flour and salt; mix to incorporate well. Pour batter into pan and bake for 25-30 minutes; top will be golden brown and spring back when lightly pressed. Remove from oven and let cool on a wire rack; do not attempt to remove the springform pan.
Step Two: The Pastry Cream
3 1/2 cups milk
4 large eggs
3/4 cup sugar
1/8 tsp salt
1/4 tsp corn starch
3 Tbsp flour
3 Tbsp cold butter, cut into small pieces
3 tsp pure vanilla extract
While the cake is baking, make the cream by first heating the milk in a large sauce pan till hot, but do not boil or scald.
While milk is heating, lightly beat together the eggs, sugar, salt; sift together the corn starch and flour and gradually mix into the wet ingredients till well incorporated.
Gradually begin mixing in the hot milk and mix together for a minute; place entire mixture back into the sauce pan. On high heat, begin whisking the mixture; it will begin to thicken and boil; continue to whisk for 3 minutes. Remove from heat, add the butter and vanilla and continue to stir until butter is completely melted and incorporated. Place mixture into a large bowl, cover with plastic wrap and refrigerate for 4 hours.
Step Three: The Chocolate Ganache
This step should not be done until you are ready to put the cake together; the chocolate cools very quickly and will harden in the pan if you wait too long to pour it onto the cake.
1/4 cup heavy cream
1 cup chopped chocolate (milk or semi-sweet is traditional; bittersweet is my personal choice)
In a small saucepan, medium heat, heat the cream until bubbles just begin to form around the rim of the pan. Add the chocolate and stir until partially melted; remove from heat and continue to stir until smooth. The ganache will thicken as it cools.
Note: to make a dipping sauce for fruit, use 1/2 cup chopped chocolate to 1/4 cup heavy cream; it will still be thick, but not harden as it cools.
Step Four: The Construction
Remove the cake from the springform pan and the parchment paper from bottom of cake; cut cake horizontally to make two separate layers; place one layer on serving platter. Evenly spread the pastry cream over this layer of cake. Place the second layer of cake over top.
The ganache should have just been made, so be ready to use a spatula to scrape it out of the pan onto the top of the cake and spread it evenly over the top. Don't worry if some of it oozes down the side; it just adds more character to your cake. The ganache will become firm quickly, so you can serve the cake immediately, or refrigerate it, so the flavors will meld together. It would be better to place a few toothpicks in the top before wrapping the cake in plastic wrap; otherwise the ganache will adhere to the wrap.