Step 1

In a 3-quart stainless-steel saucier or saucepan, combine water (or milk), butter, and salt.

Step 2

Set over high and and cook until liquid comes to a rolling boil and butter has fully melted, about 2 minutes (the small butter cubes should be fully melted just about at the same time the liquid hits a strong boil).

Step 3

Remove from heat and add flour. Using a wooden spoon or stiff silicone spatula, thoroughly mix in flour until no lumps remain (make sure to hunt down and smash out any stubborn ones).

Step 4

Return saucepan to medium-high heat and cook, stirring very frequently, until dough registers 175°F (80°C) on an instant-read thermometer; if you don't have a thermometer, other signs the dough is ready include a thin starchy film forming all over the inside of the saucier and the dough pulling together into a cohesive mass.

Step 5

To use a stand mixer: Transfer dough to a stand mixer fitted with the paddle attachment and beat at medium speed until dough registers 145°F (63°C) on an instant-read thermometer (you need the dough cool enough that it doesn't cook the eggs when they're added).

Step 6

Add eggs one at a time, making sure each is fully beaten into the dough before adding the next; it can help to start the mixer at medium-low speed for the first egg and then increase the speed to medium once the choux batter begins to develop.

Step 7

Scrape down sides of mixer bowl, then add cheese, nutmeg, and black pepper. Mix at medium speed just until cheese and seasonings are fully incorporated, about 10 seconds.

Step 8

To finish dough by hand: Let dough cool in saucepan, stirring frequently, until it registers 145°F (63°C) on an instant-read thermometer. Add eggs 1 at a time, stirring well between additions until each egg is fully incorporated before adding the next, until a smooth, shiny paste forms. Mix in cheese, nutmeg, and black pepper until well combined.

Step 9

Scrape gougères batter into a pastry bag fitted with 1/2-inch pastry tip. At this point, the gougères batter can be held in the sealed pastry bag at room temperature for up to 2 hours.

Step 10

To Bake: Adjust oven rack to middle position and preheat oven to 400°F (200°C). Line a rimmed baking sheet with parchment paper. If desired, pipe a dab of gougères batter under each of the 4 corners of the parchment to secure it in place.

Step 11

Pipe gougères batter onto parchment paper in 1 1/2-inch mounds. You should have enough batter to pipe 20 gougères.

Step 12

Using a moistened finger, gently press down any pointy tips on the mounds to smooth them out.

Step 13

Using a pastry brush, gently brush a light layer of egg wash on each mound, being careful not to let excess egg wash drip down onto the parchment. Alternatively, spray mounds lightly with nonstick cooking spray.

Step 14

Sprinkle a pinch of grated Gruyere on top of each mound, pushing down very gently to ensure it adheres to the surface.

Step 15

Bake until gougères are puffed, deeply golden brown, and feel hollow when lifted, 20 to 25 minutes. Turn off oven, crack the door open, and let stand for 30 minutes to dry and fully set the crust.

Step 16

Gougères are best served while still warm; if they cool down too much before serving, briefly reheat in a 350°F (177°C) oven before serving.