In a mixing bowl, stir together 3/4 cup milk, 3 eggs, 1/2 teaspoon Dijon mustard, 1/8 teaspoon coarse kosher salt, and 1/8 teaspoon black pepper until combined. Set aside.
Brush the wells of a cupcake pan with 1/2 tablespoon avocado oil.
Run a knife along the perforations to separate the pie crust sheet into 14 rounds. Press one round into each well of the cupcake pan.
Bake the empty shells for 10 minutes, until the bottoms take on a light golden color.
Divide 4 slices bacon, cooked and crumbled, 1 cup shredded Swiss or Cheddar cheese, and about three-quarters of the green onions evenly among the shells.
Divide the egg mixture evenly among the shells, about 2 tablespoons each.
Bake for 15 to 20 minutes, until the centers are set and the crusts are golden brown.
Scatter the reserved green onion tops over the quiches before serving.
Notes
Make ahead: bake the quiches a day early, refrigerate them in a single layer, and warm them in a 350-degree F oven for about 5 minutes before serving.Storage: leftovers keep up to 4 days in an airtight container in the refrigerator, and they freeze up to 3 months. Reheat from frozen in a 350-degree F oven for 10 to 12 minutes.