Step 1Heat the oven to 350 degrees. Lightly butter 2 (9-inch) pie pans.
Step 2Blend the flour and salt in a food processor. Add the butter and shortening, and pulse until the mixture looks like meal. Slowly add just enough cold water for the dough to come together.
Step 3Turn the dough out onto a work surface and shape it into a ball. Cut it in half and wrap each half in plastic. Refrigerate the dough for 1 hour.
Step 4Roll the dough outward from the center to 1/8 inch thickness. Place the dough in the pie pans, flute the edges and prick the bottoms with a fork. Line the dough with foil, then place dry beans or pie weights on the dough so it does not shrink.
Step 5Bake the crusts 20 minutes. Remove the beans, then bake the crusts until golden brown, another 5 minutes. Let them cool.
Step 1Heat the oven to 375 degrees.
Step 2Cook the mushrooms in the butter over medium-high heat until they have released their moisture and are lightly browned, about 10 minutes. Add the shallots and cook them until they are softened and very fragrant, about 1 minute.
Step 3Beat together the eggs and the salt. Add the sour cream and half-and-half. If you like nutmeg, add it to the batter. Beat until smooth.
Step 4Layer the cheese in the bottom of the cooled pie shells, then layer the chopped mushroom mixture, then another layer of cheese. Add the egg mixture just to the top of the cheese. Do not overfill.
Step 5Bake the quiches until the center is set and has puffed up a bit, and the quiches are lightly browned, 45 minutes. Cool before cutting.