Preheat oven to 375°F (190°C). Line two baking sheets with parchment paper.
In a medium saucepan, combine water, milk, butter, and milk. Bring to a boil. Remove from heat and let cook for a few minutes. Slowly whisk in eggs. the mix in flour until a dough forms and sticks to pan, 1-2 minutes.
Transfer dough into a pastry bag with 1/2 inch tip. Pipe walnut-sized dollops onto baking sheets about 1-inch apart. Glaze with egg yolk and sprinkle remaining cheese over.
Bake for 22-25 minutes until puffed, golden, and smell amazing. Serve hot (best) or at room temperature.