Heat oven to 325 degrees. Unfold crusts and fit each into a 9- or 10-inch deep-dish pie pan. Prick bottom of shells with a fork several times and bake for 5 minutes. Remove shells from oven and turn oven temperature up to 400 degrees.
Meanwhile, rinse greens with water, drain in colander, place in microwave-safe container with a lid and microcook on high for 8 minutes, stirring once or twice. Remove from oven and drain greens in colander. When greens are cool enough to handle, push into a pile on a cutting board and chop a bit more.
While greens are cooking, fry bacon in a 12-inch skillet until crisp, then remove bacon, pat grease off with paper towel, and dice. Leave one teaspoon bacon fat in skillet (discard or save the rest for another use) and cook onions and mushrooms until tender, about 5-7 minutes, stirring frequently.
In a large bowl, combine beaten eggs and half and half and season with nutmeg and a few grindings of pepper. Stir in cheese, chopped bacon, chopped greens and onion mixture and mix well. Fill pre-baked pie crusts with mixture, dividing equally.
Bake at 400 degrees for 15 minutes, then turn oven down to 325 degrees and continue baking for another 30 minutes, until set. Remove from oven and let rest for 10 minutes before cutting and serving.
Makes 2 quiches; serves 12.