Preheat oven to 350 degrees F.
Roll out half of pie dough and fit into a 9-inch pie plate; chill. In a skillet melt butter, add flour and whisk into a paste. Cook roux for 5 minutes or until it begins to turn lightly golden. Add onions, pepper and celery. Cook, stirring, 4 minutes, until vegetables are tender. Add crawfish, green onions, parsley and seasoning. Cook just until heated through, about 1 minute more. Let cool slightly. Roll out remaining pie dough 1/8-inch thick. Pour filling into pie shell and top with remaining dough. Crimp edges and poke a hole in top. Bake for 40 minutes, until crust is golden and filling is bubbling hot.
Combine all ingredients thoroughly.