Melt butter in large sauce pan. Add onions, bell peppers, and garlic. Saute until onions are translucent. Add file' gumbo and stir until blended well. Blend in evaporated milk, mushroom soup, rice, crawfish, salt, and black pepper. Turn heat to low. Let simmer for 5 minutes. Pour into unbaked pie crust. Top with another unbaked crust. Seal edges. Cut a slit in top crust to vent steam. Bake at 350 degrees for 50 minutes.