HEAT oven to 425°F. Prepare pie crust according to recipe directions. Roll out dough on floured surface. Cut into 12 (4-inch) circles. Press into bottom and sides of muffin cups.
COOK bacon in medium skillet over medium heat until crisp. Remove bacon from skillet with slotted spoon, reserving 1 tablespoon drippings in skillet. Add leeks. Cook over medium heat 3 to 4 minutes until tender. Remove from heat.
WHISK eggs, half-and-half, mustard, pepper and salt in large bowl until combined. Divide leeks, bacon and cheese into muffin cups. Pour egg mixture evenly over top. Bake 16 to 20 minutes or until golden brown. Cool 2 minutes. Remove from pan.