Instructions

1. Preheat the oven to 375F. Line two baking sheets with parchment paper or nonstick baking mats.
2. In a medium-sized heavy saucepan, combine 1/2 cup water with the butter and salt, and bring to a boil.
3. Turn off the heat and add the flour all at once. Stir with a wooden spoon until the dough starts to pull away from the sides of the pan and forms a lump. Set aside, without stirring, for 5 minutes, until the mixture has cooled slightly.
4. Add the eggs one at a time, mixing well after each addition. The dough will look glossy and slick at first; let it come together before adding the second egg. Stir in the mustard, cayenne and cheese.
5. Scoop up a heaping teaspoon of dough and use another spoon to scrape it onto lined pan; it should form a mound about an inch in diameter. (You could also use a pastry bag or Ziploc bag with one corner cut off, to pipe small mounds onto pan.) Repeat with the remaining dough, leaving an inch between puffs.
6. Bake the gougères until puffy and golden, about 25 minutes, rotating pans halfway through. Remove from the oven and serve immediately or at room temperature.