Make creamed fish: Scald milk with onion, carrot and bay leaf; 15 minutes. Strain.
Melt butter, add flour and blend well. Add milk and stir until smooth; add seasonings and fish.
Prepare pie pan: Line a greased deep dish with well seasoned mashed potatoes to a thickness of 1 inch.
On top of the potato layer add creamed fish to within an inch of the top. Top with another layer of mashed potatoes and top with bread crumbs and drizzle with melted butter. Bake in a hot oven until brown.