Preheat oven to 400 and line 2 baking sheets with parchment paper. Combine water, milk, butter, and salt in a medium saucepan set over medium heat. Cook for 3-4 minutes or until butter melts and the mixture comes to a boil. Lower the heat to low, add the flour, and stir for about 2 minutes with a wooden spoon until a smooth dough forms that pulls away from the side of the pan.
Put the dough in a large bowl and let cool for 1 minute. Using an electric mixer or stand mixer, beat the eggs into the dough, 1 at a time, beating thoroughly between each one. Add 1 cup of the shredded Gruyère, chives, and optional cayenne and mix just to combine.
Place dough in a large zippered bag and cut the tip off. Pipe ~1 TB of dough into mounds on the parchment lined baking pans, leaving 2” between each (you should have about 36 when you’re done). Sprinkle tops with remaining 1/2 cup shredded imported Gruyère and bake for 20 minutes or until lightly browned. Serve at once or at room temperature.
Tip: You can make these ahead of time and store in the refrigerator for 3 days or in the freezer for up to one month. Just defrost/bring to room temperature and gently reheat for a minute or two at 300 degrees in the oven or toaster oven when you’re ready to serve them!