Heat oven to 375 degrees F. On a lightly
floured board, roll out the pastry dough 1/16-inch thick.
Using a 3-inch cutter, cut out 42 circles; re-roll scraps
as needed. Fit circles into bottoms and slightly up sides
of lightly greased 2-1/2-inch muffin pans. Meanwhile, fry
bacon slices until crisp. Drain and crumble or chop. Chop
mushrooms and saute in butter until limp and liquid evaporates.
Combine bacon, mushrooms, green onion, and cheese. Divide
filling equally among muffin cups. In large bowl, beat together
eggs, add sour cream, and stir until smooth. Spoon about
1 Tbsp. into each muffin cup. Bake until puffed and light
brown, 20–25 minutes. Cool in pans 5 minutes; lift
out. Serve warm or let cool on wire racks. If made ahead,
wrap cooled quiches airtight and refrigerate overnight.
Reheat, uncovered, in a 350-degree oven for about 10 minutes.
Makes 3-1/2 dozen.