Preheat oven to 375°. On a lightly floured surface, roll dough to a 1/8-in.-thick circle; transfer to a 9-in. pie plate. Trim crust to 1/2 in. beyond rim of plate; flute edge. Refrigerate while preparing filling., Wipe mushrooms clean with a damp tea towel. Trim stems; quarter or slice large mushrooms., In a large skillet, heat 1 tablespoon butter over medium-high heat. Add leek; cook and stir 2-3 minutes or until tender. Remove from pan., In same pan, heat remaining butter over medium-high heat. Add mushrooms; cook 4-6 minutes or until tender and liquid has evaporated. Stir in leek, salt and pepper. Cool slightly., Sprinkle 1/2 cup cheese onto bottom of crust. Top with mushroom mixture; sprinkle with remaining cheese. In a large bowl, whisk eggs and cream until blended; pour over top., Bake on a lower oven rack until a knife inserted in the center comes out clean, 30-35 minutes. If desired, sprinkle with parsley before serving.