Parmesan-Onion Puffs - makes about 24 puffs

1 1/2 cups water
1 1/2 sticks unsalted butter
2 cups coarsely chopped onions
2 tsp salt
1 1/2 flour
6 eggs
1 cup freshly grated Parmesan cheese

Preheat oven to 400 degrees and grease 2 cookie sheets. Bring water to a boil in a medium saucepan and add 1 stick of the butter.
Meanwhile sauté the onions in the remaining butter until wilted, about 5 minutes. When butter has melted in the water and mixture has come to a boil again, add salt and flour all at once.
Turn the heat down to low and stir for a few minutes until mixture makes a ball and pulls away from the side of the pan. Off the heat beat in the eggs, one at a time, until each is fully incorporated before adding the next. Add cheese and onions, mixing thoroughly. Drop heaping tbsp of dough onto greased cookie sheets.
Brush tops with milk and sprinkle with additional Parmesan if you like. Bake until golden and puffy, about 35-40 minutes.