Sheet-Pan Croquembouche

Directions

1. Make the pastry cream: Add the milk to a large saucepan and set over medium-low heat on the stove; stir occasionally, to prevent any burning on the bottom, until the milk is very hot and starting to steam. While that’s heating up, combine the sugar, cornstarch, egg yolks, and salt in a bowl, and whisk until smooth. Add a splash of hot milk and whisk. Add another, bigger splash and whisk. Keep repeating this until you’ve added all the milk. Now pour this mixture back into the saucepan and cook—whisking slowly but constantly—until the mixture either comes to a boil or thickens enough for the whisk to leave a distinct trail, with a consistency that resembles pudding. Remove from heat and add the butter, vanilla extract, and bourbon. Whisk until smooth. Press the pastry cream through a fine-mesh sieve (to remove any lumps) into a heatproof bowl. Press plastic film against the custard to prevent a skin from forming. Chill until completely cold.
2. Make and bake the pate a choux: Heat the oven to 425°F. Line 2 sheet pans with parchment. Combine the water, butter, sugar, and salt in a large saucepan. Set on the stove over high heat and bring to a boil. Turn off the heat. Add the flour (yep, all at once!) and stir with a wooden spoon until smooth. Turn the heat back on to medium-low and cook, stirring constantly, for about 2 minutes, or until the mixture begins to leave a film on the bottom of the pan. Turn off the heat. Let the mixture cool for a few minutes, stirring occasionally to release steam. Once it’s slightly cooled, add one egg and mix until smooth. Repeat this until you’ve added 8 eggs. (You can do this egg-adding part in a standing mixer, but I prefer to not dirty another dish.) Beat the remaining egg with a couple grains of salt in a small bowl until smooth. Use a tablespoon-sized cookie scoop to drop the pate a choux onto the prepared sheet pans, spacing the blobs about 3 inches apart. (Overcrowding will prevent them from rising properly, so you’ll need to do 2 rounds in the oven. The dough is fine sitting at room temp, but I like to cover it with a kitchen towel or some plastic wrap.) Brush the egg wash on top of each one. Bake for 22 to 25 minutes, or until doubled in size and browned. When they come out of the oven, poke each puff’s side with a paring knife to help release steam. Scoop and bake the remaining pate a choux dough. You should get at least 54 puffs. Cool completely on wire racks before filling.
3. When the puffs are cool, fill them: You can go about this a couple ways: 1) by filling a plastic baggie with some pastry cream and snipping one of the corners or 2) fitting a piping bag with a ½-inch plain tip and filling that. Both work, so totally your call. Remember that steam vent in each puff? That’s your pastry cream’s entry point. Fill each puff.
4. Re-line one of the sheet pans with a fresh sheet of parchment. Now fill it with the cream puffs; with 54 puffs, it’ll be 9x6 puffs.
5. Make the caramel: Combine the sugar and water in a saucepan. Set over medium-heat heat. Fill a small dish with water; if you see any sugar grains creeping up the sides of the pan, dip a pastry brush in the water, and brush away the grains (this prevents crystallization). When the sugar turns from cloudy to clear, add the vinegar. Continue to cook until the sugar caramelizes and turns amber. You want to cut the heat *before* it reaches your dream color (a rich brown), since it will significantly continue to darken as it cools. (If you’re worried about taking it too far or not confident in the timing, you can fill a bowl with ice water and bobble the saucepan in there to halt the cooking.)
6. Top the puffs: Let the caramel cool for about 5 minutes, or until it’s no longer bubbly and about the thickness of maple syrup or runny honey. (If you top the puffs when the caramel is too warm and liquidy, it won’t form the same thick layer on top of the puff.) Use a heat-proof spoon to top each cream puff with a lid of caramel; you don’t want too much to drip down, or else the puffs will become problematically adhered to each other. Sprinkle each caramel-topped puff with flaky salt before the caramel hardens. After you’ve topped each puff, you should have some caramel leftover. Use the spoon to wave caramel back and forth, all around the sheet pan, to create thin strands. Let cool for a few minutes until the caramel is totally hard, then serve.