2-inch round cutter; a large pastry bag fitted with an open tip #808; open star tip
Arrange a rack in the middle of the oven and preheat to 375 degrees F. Line a baking sheet with parchment paper. Place a stand mixer bowl and whisk attachment in the freezer for your filling.
For the craquelin: Add the butter and sugar to a second stand mixer bowl fitted with the paddle attachment and beat until combined. Add the flour and beat to combine. Stir in a few drops of food coloring of choice and beat until uniform in color. Scoop the paste out onto a sheet of parchment paper with a rubber spatula. Cover with another piece of parchment paper and use your hands to press out into an even sheet. Then roll gently a few times with a rolling pin to flatten to an even 1/8-inch thick. Transfer to a baking sheet and freeze for 20 minutes. When the craquelin is frozen, remove it from the freezer. Peel the top piece of parchment off and cut rounds with a 2-inch round cutter.
For the choux dough: Combine the butter, sugar, salt and 1 cup water in a medium saucepan over low heat. Once the butter has melted, bring it to a boil over medium heat. As soon as it boils, remove the pan from the heat and sift the flour directly into the pan. Stir the batter into a paste with a wooden spoon; you will have to beat it hard. Return the pan to medium heat. Stir the batter continuously until it pulls away from the sides of the pan and is slightly shiny, about 3 minutes.
Transfer the batter to a stand mixer bowl fitted with the paddle attachment and beat until slightly cooled, about 3 minutes. Add the eggs, one at a time, incorporating each one thoroughly before adding the next.
Fit a large pastry bag with tip #808 and fill with the choux dough. Pipe twelve 2-inch circular mounds, about 2 inches apart, onto the prepared baking sheet. If the batter has a peak, dab it smooth with a wet fingertip.
Beat the egg yolk with 1 tablespoon water and brush the surface of the puffs with the beaten yolk. Using a small offset spatula, gently lift the craqulin rounds off the parchment and place on top of the cream puffs. Bake on the middle rack for 20 minutes, then reduce the oven temperature to 325 degrees F and continue baking until the puffs are golden brown, light, airy and crisp, 30 to 35 minutes more. If the cream puffs still don't feel completely dry and crisp at the end of the baking time, poke a hole in the bottom with a paring knife and place them back into the oven for a few more minutes to crisp up. Remove from the oven and cool completely on a wire rack.
For the filling: Remove the stand mixer bowl and whisk attachment from the freezer. Add the cream cheese and sugar to the bowl and beat on high speed until completely combined. Add the heavy cream and vanilla and mix on low speed until mostly combined. Increase the speed to high and whip until soft peaks form. Add the dulce de leche (or your flavoring of choice) and beat until stiff peaks form. If you would like to tint your cream filling, add a few drops of food coloring at this point.
To assemble: Cut the puffs in half with a serrated knife and set the tops aside. (If the puffs are very moist inside, scoop out the excess dough and re-crisp them in a 350 degree F oven for about 5 minutes. Cool completely before continuing.) Pipe with an open star tip or spoon the whipped cream filling into the bottom halves of the cream puffs. Replace the puff tops. Pipe a small star or dollop of whipped cream on top and decorate as desired with berries or melted chocolate.