Preheat oven to 375 degrees. Mix butter, finely chopped scallion and 1/4 cup shredded Cheddar cheese into the mashed potatoes. Season with salt and pepper to taste; set aside.
Heat oil in a large frying pan. Add onion and cook until dear. Add grcmnd beef and cook until well browned. Pour off excess fat, then stir in flour and cook 1 minute. Add ketchup and beef broth. Bring to a boil, reduce heat and simmer for 5 minutes.
Spread the ground beef in an even layer on the bottom of a 2 quart casserole dish. Next, spread a layer of frozen peas and carrots. Top with the mashed potato mixture and sprinkle with remaining shredded cheese. Sprinkle paprika over top.
Bake in the preheated oven for 20 minutes, or until golden brown. Serve immediately. Makes 8 servings. Enjoy!