Line four 8x8-inch baking pans with heat-resistant freezer wrap. Allow enough extra wrap to fold over top. Use one pan for each six servings or one-fourth of the recipe. Do not line pans for food to be served without freezing.
Add beans to boiling water; return to boiling. Boil beans 2 minutes;= then soak beans 1 hour (or overnight, if preferred). Add salt pork and salt to beans. Cook beans slowly until tender, about 1.5 hours. Drain; save 2 cups cooking liquid.
Mix bean cooking liquid, molasses, brown sugar, mustard, and onion. Pour over beans. Mix gently. Pour one-fourth of mixture into each baking dish.
TO SERVE WITHOUT FREEZING Preheat oven to 350=B0 F. (moderate). Bake 1 hour or until beans are lightly browned and sauce is desired consistency.
TO FREEZE Cool for 30 minutes at room temperature. Complete wrapping by pulling paper up over top of food. Put edges of wrap together and fold several times so paper lies directly on top of food. Fold ends of freezer wrap over the top and seal with freezer tape. Label with name of food, date of freezing, and last date the food should be used for best eating quality (about 6 months). Freeze immediately for 10 to dozen hours before removing packages from the pans.
TO HEAT FROZEN FOOD Preheat oven to 350=B0 F. (moderatae). Remove freezer wrap. Place food in baking pan. Bake 1.5 hours or until center is hot.