For the Cheese Puffs:
- 1⅓ cups water, plus more for smoothing
- 1 tablespoon granulated sugar
- 1 teaspoon kosher salt
- 1½ sticks unsalted butter
- 1¼ cups all-purpose flour
- 5 eggs
- 1 cup finely grated Gruyère cheese, divided
For the Buffalo Cheese Sauce:
1. Make the cream puffs: Preheat the oven to 400º. In a medium saucepan, combine the water, sugar, salt and butter. Bring to a simmer over medium-high heat. Once simmering, reduce the heat to medium and add the flour. Using a wooden spoon, stir the mixture constantly until it’s thick and a thin film forms on the bottom of the pan, 4 to 5 minutes.
2. Transfer the mixture to the bowl of a stand mixer fitted with the paddle attachment and mix for 2 more minutes to slightly cool down the dough. One at a time, add the eggs, making sure each one is completely incorporated before adding the next. Add half of the cheese to the batter and mix to incorporate. Transfer the pâte à choux batter to a piping bag fitted with a ⅝-inch round tip (#808 tip).
3. Line 2 sheet pans with parchment paper and pipe 1-inch rounds of dough 1½ inches apart. Each puff will have a tail at the top where you piped it, so dip your finger into a small bowl of water and smooth the tail for a perfect round. Sprinkle each puff with ½ teaspoon of the remaining grated Gruyère.
4. Bake for 10 minutes, then rotate the trays and reduce the temperature to 375º. Continue to bake until golden brown and puffed, another 20 minutes.
5. Meanwhile, make the Buffalo cheese sauce: In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook until a blond paste forms, 2 to 3 minutes.
6. Slowly whisk in the milk until smooth, then add the garlic and thyme, and bring to a simmer. Cook, stirring often, until thickened, 5 minutes. Whisk in the cheeses and hot sauce until smooth, 1 to 2 minutes, then remove from the heat and season with salt. Transfer to a squeeze bottle or piping bag fitted with a small round tip.
7. Let the puffs cool for 5 minutes, then puncture a small hole in the bottom of each one using a ⅛-inch star tip or paring knife. Fill each puff with the cheese sauce, then transfer to a platter and serve.