Soak codfish in water 2 hours, changing water 3 times.
Cover with fresh water and simmer until it is tender and can be shredded (about 10 minutes).
Drain.
Cook salt pork in frying pan until crisp.
Remove salt pork and all but 3 tablespoons of fat.
Cook onion until tender but not browned.
Blend in flour and pepper and let bubble.
Gradually stir in milk and cook and stir until mixture boils and is thickened.
Add codfish, salt pork and potatoes.
Pour mixture into buttered 1 1/2 -quart baking dish.
Sift flour, baking powder and salt together.
Cut in shortening with pastry blender or two knives until texture of corn-meal.
Stir in milk until flour is moistened.
Pat out 1/2 inch thick on lightly floured board and with a biscuit cutter cut into biscuits.
Put biscuits on top of fish mixture in casserole.
Bake in a 450° F.oven 15 minutes or until hot and biscuits browned.