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.