Caramelized-Onion, Spinach, and Bacon Quiche Cups

Makes 6 servings. Olive oil cooking spray 1 (10 ounce) package frozen chopped spinach – thawed, drained and squeezed dry 1/4 cup low-fat sour cream 2 tablespoons minced shallots 1 cup evaporated skim milk 1/4 teaspoon salt 1/8 teaspoon pepper 2 egg whites 1 egg 3/4 cup Caramelized Onions (about 3 cups