Heat milk on a double-boiler while roux is being prepared. Blend flour and butter and heat to simmer for three minutes. Add to the hot milk, add the spices, and stir briskly. Increase the double-boiler heat to medium high and cook for 15 minutes. Add the Gruyere and stir until melted. Reserve the sauce.
Mix the macaroni, chanterelles, peas, 1 cup Gruyere, and parsley with the reserved sauce and portion into baking vessels.
Sprinkle the 1/2 cup of cheese over the casserole. Mix the butter with the bread crumbs and sprinkle evenly over the casserole. Pour the cream over all. Bake at 375 degrees F for 35 minutes, or until golden brown and bubbly.