Profiteroles are a French classic dessert featuring choux pastry, which bakes into light golden puffs. Sandwich your favorite ice cream into the halved pastry puffs, then drizzle them with a decadent drizzle of chocolate sauce.
Make the choux pastry: Preheat the oven to 400˚ F. Line a baking sheet with parchment paper or a silicone baking mat. Combine the milk, water, butter and salt in a medium saucepan and cook over medium heat until the liquid is shimmering and the butter is melted, 2 to 3 minutes. Add the flour and stir to form a dough. Cook, stirring, until the dough releases from the sides of the pan and the flour smells slightly nutty but doesn’t brown, about 3 minutes.
Transfer the dough to a large bowl, add 1 egg and beat with a mixer on medium-high speed until fully combined. Beat in the remaining 3 eggs, one at a time, to make a sticky, glossy dough.
Transfer the dough to a pastry bag fitted with a 1/2- or 3/4-inch round tip. Pipe mounds of dough on the baking sheet, 1 to 1 1/2 inches wide and about 1 inch high, spacing them 1 inch apart; press down the pointy tops with a wet finger. Bake until deep golden and crisp, 25 to 30 minutes. Transfer to a rack and let the pastry puffs cool completely on the pan.
Make the chocolate sauce: Put the chocolate in a heatproof bowl. Bring the heavy cream and corn syrup to a simmer in a small saucepan over medium heat. Immediately pour over the chocolate and cover the bowl; let sit 5 minutes, then whisk until smooth.
Assemble the profiteroles: Cut the pastry puffs in half horizontally. Fill the bottoms with medium-size scoops of ice cream (about 3 tablespoons each). Cover with the tops and spoon the chocolate sauce all over. Serve immediately.