About 1 1/2 hours before serving, combine ground beef, bread crumbs, allspice, nutmeg, pepper and 1 tsp salt by hand. With fingers, press mixture to bottom and side of 9" pie plate just to rim; refrigerate. In large bowl, using a potato masher, mix sweet potatoes with remaining ingredients and 1/2 tsp salt until smooth. Spoon sweet potato mixture into pie shell, spreading to edge to seal. Bake in a 400 degree oven about 50 minutes or until knife inserted in center comes out clean. Makes 6 servings.