Heat the butter in a saucepan until it bubbles. Add all the sauce ingredients except the milk and flour, and sauté until the vegetables are well browned and sticking a little bit to the pan. Remove from heat and set aside for 15 minutes.
After 15 minutes, add the evaporated milk and 3/4 cup of water to the saucepan. Bring to a boil, stirring lightly.
While the boil is coming up, whisk the flour into 3 oz. of water. After the pan comes to a boil, stir the flour-water mixture slowly into the other ingredients. Simmer for three minutes, until the sauce is thick.
Spoon the sauce into a pan and refrigerate until it thickens, or overnight.
To complete the dish, preheat the oven to 425 degrees. Mix the bread crumbs, Parmesan cheese, and paprika.
Divide the crabmeat among four to six scallop shells or small au gratin dishes. Top with about 1/4 cup of the chilled sauce. Sprinkle with a heaping Tbs. of the bread crumb mixture. Bake at 425 degrees until the crumbs brown and the sides of the dish begin to bubble--20-25 minutes.
Remove from the oven and top with 1 tsp. melted butter. Serve very hot.