Instructions

1. To make the pastry cream: Heat the half-and-half, 6 tablespoons of the sugar, and the salt in a medium saucepan over medium heat until simmering, stirring occasionally to dissolve the sugar.
2. Meanwhile, whisk the egg yolks in a medium bowl until well-combined. Whisk the remaining 2 tablespoons sugar into the eggs, and whisk until the sugar has begun to dissolve and the mixture is creamy, about 15 seconds. Whisk in the cornstarch until combined and the mixture is pale yellow and thick, about 30 seconds.
3. When the half-and-half mixture reaches a full simmer, slowly whisk the simmering half-and-half into the yolk mixture by the ladleful to temper the eggs. Return the mixture to the saucepan, scraping the bowl with a rubber spatula. Return the mixture to a simmer over medium heat, whisking constantly, until a few bubbles burst on the surface and the mixture is thickened and glossy, about 30 seconds. Off the heat, whisk in the butter and vanilla. Strain the pastry cream through a fine-mesh sieve set over a medium bowl. Press plastic wrap directly on the surface to prevent a skin from forming and refrigerate until cold and set, at least 3 hours or up to 2 days.
4. To make the cream puff shells: Beat the eggs and egg white in a liquid measuring cup until combined. You need ½ cup - discard the excess. Set aside. Ready your food processor, fitted with the steel blade. Grease the bottom of a large baking sheet with butter or cooking/baking spray and the line baking sheet with parchment paper.
5. Bring the butter, milk, water, sugar, and salt to a boil in a small saucepan set over medium heat. Once the mixtures fully boils and the butter is melted, immediately remove the pan from the heat and beat in the flour with a wooden spoon until it combines and clears the sides of the pan.
6. Return the pan to low heat and using a heatproof rubber spatula, cook the mixture while you stir it constantly with a smearing motion on the bottom of the pan. Continue this for about 3 minutes. The mixture should be slightly shiny, look like wet sand, and tiny beads of fat from the butter should appear on the bottom of the saucepan. If you have an instant thermometer, the temperature should read 175° to 180° F.
7. Immediately transfer the mixture to the food processor. Leave the feed tube open and process (not pulse) for 10 seconds. With the machine running, gradually add the eggs through the feed tube in a steady stream. When the eggs have been added, stop processing and scrape down the sides of the bowl. Process for another 30 seconds, until the mixture turns to a thick, smooth, and sticky paste.
8. Preheat the oven to 425° F with a rack in the center of the oven. Fill a pastry bag fitted with a ½-inch round tip with the paste. Pipe the paste into 24 1½-inch rounds on the baking sheet. Dip the back of a small spoon in some cold water and gently smooth out the irregular tops of the rounds.
9. Bake for 15 minutes then reduce the oven temperature to 375° F - do not open the oven door. Bake for another 10 minutes until the puffs are golden brown and fairly firm - they should not be soft and squishy. Transfer the baking sheet to a wire rack and using a clean kitchen towel, hold each puff while you slide a ¾-inch slit into the side to allow the steam to escape with a paring knife. Return the baking sheet to the oven, prop the door open with a wooden spoon, and allow the puff to dry out and crisp up for about 45 minutes. Transfer the puffs from the baking sheet to a wire rack to cool completely.
10. To assemble the cream puffs: Once the pastry cream has chilled for at least 3 hours, slice a small X into the side of each pastry puff. Fill a pastry bag fitted with a ¼-inch round tip with pastry cream and pipe some cream into the X of each pastry puff. You'll know when you've piped enough cream because the cream will start to either push out the opposite side of the puff or it will start to push the pastry bag out. Dust the tops of the filled cream puffs with some sifted powdered sugar and serve immediately.

Storage and Do ahead: You can store the unfilled cream puff shells (at the end of Step 9) at room temperature for up to 24 hours or freeze them for up to 1 month. If you freeze them, thaw them at room temperature then heat them on a baking sheet at 300° F for 5 to 8 minutes, until crispy.

Alternatively, the cream puffs can be fully assembled in advance, frozen, and thawed without issue. I tested doing this and the only issue I found when thawed is that the pastry shells aren't crispy any longer. It didn't deter from the taste at all, and the pastry cream was still delicious, so if you're OK with a soft cream puff this would be a great make-ahead dessert.