PLACE potato chunks in medium saucepan. Cover with water; bring to a boil. Cook over medium-high heat for 10 to 15 minutes or until tender; drain. Return potatoes to saucepan; add 1 cup pumpkin, 1/4 cup cheese, 1/4 teaspoon salt and 1/4 teaspoon pepper. Beat with hand-held mixer until smooth. Cover.
MEANWHILE, HEAT oil in large skillet over medium-high heat. Add onion and carrots; cook, stirring occasionally, for 5 minutes or until carrots begin to soften. Stir in beef, flour, garlic powder and remaining 1/4 teaspoon salt and remaining 1/4 teaspoon pepper. Cook, stirring occasionally, for 3 to 4 minutes or until beef is no longer pink. Stir in broth, remaining pumpkin and Worcestershire sauce; bring to a boil. Cook, stirring occasionally, for 2 to 3 minutes or until mixture has thickened slightly.
SPOON beef mixture into ungreased 9-inch deep-dish pie dish or other broiler-proof casserole dish (1 1/2- to 2-quart). Spoon pumpkin-potato mixture evenly over beef filling, spreading gently. Sprinkle with remaining 1/4 cup cheese.
BROIL for 5 minutes or until cheese is lightly browned.