Pâte à Choux
½ cup water
½ cup whole milk
1 stick (8 tablespoons) unsalted butter
1 teaspoon vanilla extract
1 tablespoon granulated sugar
¼ teaspoon kosher salt
1¼ cups all-purpose flour
5 large eggs, divided
1 large egg yolk
Dulce de Leche Cream
1 vanilla bean, halved lengthwise
2 cups store bought or homemade dulce de leche
1 teaspoon ground cinnamon
½ teaspoon kosher salt
1½ cups mascarpone
Confectioners’ sugar, for dusting
1. Make the Pâte à Choux: Preheat oven to 425° and position two racks in the lower half of the oven. In a medium saucepan set over medium heat, add the water, milk, butter, vanilla, sugar and salt and bring to a boil. Once the butter is melted, add the flour all at once and use a wooden spoon to vigorously stir the flour into the liquid. As the dough thickens, continue stirring until the mixture pulls away from the sides of the pan and is slightly dried out, about 3 minutes.
2. Transfer the dough to the bowl of a stand mixer fitted with a paddle attachment and turn on to high speed. Mix until the dough stops steaming, about 5 minutes. Add the whole eggs (save the egg yolk for later), one at a time, waiting to add the next until the previous egg is completely incorporated into the dough. Transfer the dough to a large piping bag (the dough can be stored, covered in the refrigerator for up to 1 day at this point).
3. Line two baking sheets with parchment paper. Use scissors or kitchen shears to snip the tip of the bag and pipe the pâte à choux into small 1½-inch mounds (each about 2 tablespoons of paste), spacing the pâte à choux puffs 1½ inches apart. Dip your finger in a bit of water and press down to smooth the peaks on the pâte à choux circles (the peaks can burn during baking). In a small bowl, whisk in the remaining egg yolk with a fork. Use a pastry brush to brush the egg wash lightly over the puffs.
4. Place the baking sheet in the oven and bake for 15 minutes, then lower the oven to 300° and bake until the puffs are browned and dry, about 10 minutes longer. Remove the pâte à choux puffs from the oven and cool to room temperature.
5. Make the dulce de leche cream: Lay the vanilla bean halves on a cutting board and use the tip of a paring knife to remove the seeds. Place the seeds into a medium bowl. Add the dulce de leche and whisk until smooth. Stir in the cinnamon and salt. Add mascarpone and use a spatula to gently fold together until just combined. Transfer the dulce de leche cream to a large piping bag fitted with a medium tip.
6. Use a skewer or a paring knife to poke a small hole in the bottom of each puff and insert the tip of the piping bag into the puff. Fill with the dulce de leche cream until the puff is full and repeat with the remaining puffs. Dust with confectioners’ sugar. Arrange the filled puffed on three-tiered cake plates and serve.