Cut squash into large pieces and steam until tender. Remove cooked squash from shells; measure 4 cups pulp and reserve remainder for another dish. Process squash in a food processor with a metal blade until pureed. Set aside. In a large ssaucepan or dutch oven, melt margarine; saute onion and carrots for about 5 minutes or until tender but not brown. Stir in broth, salt, pepper and nutmeg; bring to boiling. Reduce heat to simmer, stir in squash puree and milk. Simmer 5 minutes or until heated through. Adjust seasonings as necessary. Spoon 2 tablespoons of the cranberry sauce in the center of each bowl of soup.