Step 1

Preheat an oven to 425◦F degrees. Line two baking sheets with parchment paper or Silpats.

Step 2

Combine water, butter, salt and sugar in a saucepan over medium heat. Bring to a boil and stir occasionally. At boil, remove from heat and sift in the flour, stirring to combine completely.

Step 3

Return to heat and cook, stirring constantly until the batter dries slightly and begins to pull away from the sides of the pan.

Step 4

Transfer to a bowl or stand mixer fitted with the paddle attachment, and stir 1 minute to cool slightly.

Step 5

Add 1 egg and mix. The batter will appear loose and shiny at first. As you stir, the batter will become dry-looking like lightly buttered mashed potatoes. It is at this point that you will add in the next egg. Repeat until you have incorporated all the eggs.

Step 6

Transfer batter to a pastry bag fitted with a ½-inch round open tip (or directly from the bag opening without a tip). Pipe 13-15 choux about 1 inch-part in a baking sheet. Choux should be about 1 1/2 inches wide. Repeat the process on the second sheet.

Step 7

Using a clean finger dipped in hot water, gently press down on any tips that have formed on the top of choux when piping. You want them to retain their ball shape, but be smoothly curved on top.

Step 8

Brush tops with egg wash.

Step 9

Bake the choux at 425◦F until well-puffed and turning lightly golden in color, about 10-12 minutes. Lower the temperature to 350◦F degrees and continue baking until well-colored and dry, about 18-20 minutes more. Remove to a rack and cool.

Step 10

In a medium bowl, whisk cornstarch in 1/4 cup of the heavy cream, set aside. Combine the remaining heavy cream, sugar and 1/2 cup champagne in a saucepan; heat until the mixture just starts to bubble – don’t let it boil or most of the champagne flavor will cook out. Once the sugar is dissolved, remove from heat. Let cool 5 minutes.

Step 11

Beat the whole egg and egg yolks into the cornstarch/heavy cream mixture. Pour the mixture into the saucepan in a thin stream while whisking constantly and vigorously. Return the pan to the heat and cook, whisking constantly until thickened. Remove from heat and beat in the butter and vanilla.

Step 12

Pour the mixture into a bowl and cover the surface with plastic wrap. Refrigerate until firm and well set, about 4 hours.

Step 13

When the pastry cream is set, give it a stir and transfer to a disposable piping bag with a ½-inch hole snipped in the end. (Or fit with ½ inch decorator piping tip.) Cut a slit in the bottom edge of each choux pastry shell and fill with the pastry cream.

Step 14

Place the chocolate and cream in a medium microwave-safe bowl. Heat at 100% power in the microwave for 1 minute. Let the mixture stand for 1 minute.

Step 15

Whisk together until a smooth, shiny ganache forms. Dip the tops of each puff into the ganache and replace on the baking sheet or on a wire rack. Immediately top with star sprinkles, if using.

Step 16

Leftovers will keep in the refrigerator for up to 2 days. While the choux pastry shells may lose some crispness, the flavors remain delicious!