1 medium-sized onion, peeled and ½ tsp dry mustard cut into ¼-inch-thick slices ½ tsp paprika 1½ pounds smoked haddock ¼ tsp ground hot red pepper 3 c milk (cayenne) 4 T butter 1 tsp salt 2 T finely chopped scallions, ¼ c flour white part only 1 c light cream ½ c finely chopped red bell 1 T pale dry sherry pepper 2 tsp Worcestershire sauce ¼ c finely chopped green bell 6 slices white bread, trimmed of pepper crusts, toasted and each cut diagonally into 4 triangles ------------------------------Place the onion slices in a heavy 10-inch skillet, set the smoked haddock on top and pour in 2 cups of the milk. The milk should cover the fish completely; add more if necessary. Bring to a boil over high heat, reduce the heat to low and cover the skillet tightly. Simmer undisturbed for 10 to 15 minutes, or until the fish flakes easily when prodded with a fork. Do not overcook. With a slotted spatula, transfer the smoked haddock to a plate. Then break the fish into large flakes with a fork, picking out and discarding any bones you find. Discard the milk and onions.
In a heavy 10- to 12-inch skillet, melt the butter over moderate heat. When the foam begins to subside, add the scallions and stir for a minute or so until they are soft but not brown. Add the chopped red and green pepper, the mustard, paprika, ground red pepper and salt, and cook, until the vegetables are soft. Add the flour and mix well.
Then, stirring the mixture constantly with a wire whisk, pour in the cream and the remaining 1 cup of milk in a slow, thin stream. Cook over high heat until the sauce comes to a boil and thickens heavily. Reduce the heat to low and simmer for 3 minutes, thenn stir in the haddock, sherry and Worcestershire sauce and simmer until the fish is heated through.
To serve, arrange the toast triangles attractively on six heated plates and ladle the deviled finnan haddie over them. Serves 6.