Boston Cream Pie Cupcakes

These little guys are so delicious. It looks like a regular yellow cupcake with chocolate frosting, and then BAM- a sweet vanilla pastry cream is shoved inside! you could totally do this as a cake as well (obviously since that's the normal way to do it), but this recipe makes 24 cupcakes and a smidge more for a baker's treat! You do want to make the pastry cream in advance so that it has time to cool off before filling the cupcakes.

For the Pastry Cream:

1 2/3 c heavy whipping cream *I usually do half milk and half whipping cream, but I only had whipping cream at home, so I did all whipping cream, and it was delicious 

½ c granulated sugar

Pinch of salt

4 large egg yolks

½ c flour

4 tbsp unsalted butter, cold

1 tsp vanilla extract 

1. In a medium heat-proof mixing bowl, whisk together egg yolks, salt, and sugar until completely combined and a bit frothy. *If you're doing this alone, use your stand mixer bowl. This way you can stick it on the base so that it doesn't move later when you need to pour and whisk at the same time.

2. Add flour and set aside while heating cream.
3. Heat heavy cream and butter on the stove until simmering. Take off the heat when mixture starts to simmer *you don’t want it to boil.
4. Slowly add cream mixture into the egg yolk mixture, stirring constantly. Whisk well. *Be gentle- you don’t want to cook the eggs, so baby steps here, folks.
5. Return the mixture to the pan and bring to a simmer, stirring constantly. The mixture will thicken within a few minutes. Take off heat once it’s thick and add in vanilla extract.  
6. Cool to room temperature and transfer into a bowl with a lid to be refrigerated. It needs to cool at least four hours or overnight.
**I actually had to do my pastry cream twice because I fucked it up the first time. I think I heated the mixture too hard and fast the first time, and then my pastry cream was all weepy (see left picture). The second time, I went slower, lifting the pan off the heat every once in a while so that my cream didn't get too hot too fast. See right picture for pretty pastry cream. 

 

For the Cupcakes:
1/2 c vegetable oil
1/2 c unsalted butter (1 stick), room temp
2 c granulated sugar
3 eggs, separated
1 tsp vanilla extract
2 c all-purpose flour
1 1/2 c cake flour

1 tsp salt
1 1/2 tsp baking powder
1 1/2 tsp baking soda
1 1/2 c buttermilk


1.Preheat oven to 350F and prepare cupcake pans with liners and grease a small (I usually do 6 in) pan for the extra batter.
2. In a stand mixer fitted with paddle attachment, cream together oil, butter, and sugar. Add in the yolks of the three eggs- keep the whites separate. Add in vanilla extract.
3. In a small bowl, whisk together egg whites until at stiff peaks. Set aside.
4. In a separate bowl, combine all dry ingredients- flour, baking powder, baking soda, and salt.
5. Pour 1/3 of the dry ingredients into the sugar mixture and mix to combine.
6. Pour 1/2 of the buttermilk into sugar mixture and combine.
7. Pour another 1/3 of dry.
8. Pour second 1/2 of buttermilk.
9. Pour in the last 1/3 of the dry ingredients.
10. Slowly fold in the egg whites that were whipped up earlier. *This ensures that the batter will be light and fluffy.

11. Distribute into pans and bake for 18 - 22 minutes or until a toothpick inserted comes out clean. 

12. Allow to cool completely before filling with pastry cream.  

For the Frosting: 
4 sticks unsalted butter, room temperature
1 c cocoa powder
1/8 c black cocoa powder *if you don't have this, it's fine- you can just add a bit more cocoa powder- this just makes it a little darker and richer.
4 c powdered sugar
1/4 tsp salt
1 tsp vanilla

1. Sift together powdered sugar and cocoa powders in a large bowl.
2. In a stand mixer with paddle attachment, cream butter.
3. Slowly add powdered sugar and cocoa powders to the butter.
4. Add salt and vanilla and mix to incorporate.
5. If it seems too loose, add a bit more cocoa powder; if it seems really tight, you can add a bit of heavy cream or buttermilk to it.

Assembly:
1. Take a pairing knife and cut out the center of each cupcake, making sure to not go all the way to the bottom of the cupcake.
2. Place cooled pastry cream in a piping bag or a ziploc bag with the corner cut off. Fill each cupcake hole with pastry cream.

3. Place buttercream in a piping bag and snip the end off. Starting from the outside, pipe around until you have the cupcake and the cream covered. *You can also use a different tip if you want, but I just went for the straight swirl. I would say it's easier to do this with a piping bag instead of just an offset spatula because you have that pastry cream sticking out of the top of the cupcake.

4. Serve immediately- if you have leftovers or are making these ahead of time, put them in the fridge since they have the pastry cream in them. When you go to serve, just take out of the fridge about 30 minutes beforehand and they'll warm back up to room temp.