INGREDIENTS
1
recipe pie dough (see Pâte Brisée recipe)
2 tbsp
olive oil
2
large red onions (about one pound total), French-cut (see below)
Salt and freshly ground pepper
2
teaspoons balsamic vinegar
3/4
cup milk
1/4
cup heavy cream
3
large eggs
nutmeg
6 oz
Gruyère cheese, grated (1 1/2 cups)