gluten free mini boston cream whoopie pies.

for the pastry cream

1. Line a half-sized baking sheet with plastic wrap, allowing enough wrap to reach the other end of the baking sheet to hang off the edge of the pan.
2. Set the half baking sheet over a larger baking sheet, or a deep casserole dish filled with ice. Take care that whatever larger container you use will allow the baking sheet to come completely in contact with the ice. Set aside.
3. Combine the milk and first amount of sugar in a medium sized heavy saucepan, and set over medium-high heat, stirring occasionally.
4. In a medium sized heat-safe bowl, whisk together the egg yolks, whole egg, the second amount of sugar, and the cornstarch. Whisk until smooth, about 30 seconds. Set aside.
5. When the milk and sugar have reached a low boil, remove from the heat.
6. Whisking the egg mixture continuously, slowly pour the milk into the bowl to temper the mixture. Take care not to do this too fast, otherwise the mixture will curdle.
7. When all of the milk has been tempered into the egg mixture, pour the entire contents of the bowl back into the saucepan and place over medium high heat.
8. Whisking constantly, allow the mixture to come to a boil and thicken, approximately 30 seconds to 1 minute.
9. When the mixture has thickened, add the first amount of butter and vanilla extract, whisking to combine.
10. Immediately pour the pastry cream through the fine mesh sieve onto the baking sheet lined with plastic wrap. Spread the pastry cream in an even layer on the baking sheet, and cover with plastic wrap, taking care to remove as many of the air bubbles as possible.
11. Allow the mixture to cool for 30 minutes, then transfer to the bowl of a stand mixer with the whip attachment fitted on.
12. Whip the pastry cream on medium speed until it reaches a smooth, fluffy consistency, about 5 minutes.
13. With the mixer on low, add the last quantity of butter. Return the mixer to medium speed and beat 1 minute, or until smooth and all of the butter is incorporated.
14. Transfer the pastry cream to an airtight container and refrigerate at least one hour before using.
15. The pastry cream will keep, stored in an airtight container in the fridge for about 1 week.

for the whoopie pies

1. Preheat the oven to 325 degrees F, with a rack in the center of the oven.
2. Line a baking sheet with parchment paper and set aside.
3. In a medium sized bowl, combine the gluten free flour, cornstarch, xanthan gum, baking powder, baking soda, salt, and brown sugar. whisk to combine, taking care to ensure there are no lumps.
4. In a small bowl, combine the cooled melted butter and egg, whisking until smooth.
5. Add the butter and egg mixture to the dry ingredients. Using a silicone spatula, stir to combine.
6. Add the buttermilk and vanilla bean paste to the batter, stirring with the spatula until smooth.
7. Using a small cookie scoop (holds 2 teaspoons of batter, so if you don't have a scoop just use a teaspoon!), portion the batter onto the prepared baking sheet, leaving about an inch and a half of room in between each one.
8. Bake at 325 degrees F for 12-15 minutes, rotating the baking sheet in the oven halfway through the baking time.
9. When the whoopie pies are pale golden brown and spring back when lightly touched, remove from the oven and allow to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
10. The whoopie pies can be made two days in advance, stored at room temperature in a single layer in an airtight container.

for the chocolate ganache

1. Place the chopped chocolate in a heat-safe bowl and set aside.
2. Heat the heavy cream in a small saucepan over medium heat, until steaming but not boiling. Small bubbles will form around the edges of the pan.
3. Remove from the heat and pour over the chopped chocolate. Allow to stand for 30 seconds before whisking vigorously until ganache is smooth and combined.
4. Allow to sit at room temperature for 5-10 minutes to thicken slightly before using.

assembling the whoopie pies

1. Using a small cookie scoop or a teaspoon, place a dollop of pastry cream in the center of one of the whoopie pies, rounded side down. Place another whoopie pie on top and press down slightly to sandwich.
2. Drizzle the tops of each completed whoopie pie with the cooled and slightly thickened ganache.
3. Top with sprinkles, if desired.
4. Serve immediately!