Add bell pepper, onion and celery to butter and saute until tender. Add crawfish fat and simmer covered 10 minutes. Add crawfish tails, green onions and remainder of seasonings. Thicken if necessary with a little cornstarch and let cook long enough to thicken gravy.
Using your favorite pie crust recipe, make enough pie dough for a double crust pie. Place the dough in a 9-inch pie pan. Gently press the dough to the bottom and sides. Cut excess dough, leaving a 1-inch overhang. Fill the pie shell with the cooled filling. With a pastry brush, dip in cold water and moisten the outside edge of the pastry shell. Place top crust over the filling, cutting off the overhang even with the overhang on the bottom crust. Crimp the top and bottom crusts together, trim. Cut 2 or 3 one-inch parallel slits in the top of the pie. Place pie in a preheated 450 degree oven and bake for 10 minutes, then lower heat to 375 degrees and cook for 35 minutes longer or until crust is a golden brown. Serve hot as a main course.
Using the same procedure, individual pie pans or a muffin pan with large cups can be used instead of a large pie pan. Roll the dough, fit into the cups, place the filling in the cups. Moisten the edges with cold water. Place a circle of dough on top. Crimp edges together. Cut a 1-inch slit in the center. Bake as above.