- 5 potatoes, peeled and cubed
- 1/2 cup margarine, divided
- 1/3 cup milk, or as needed
- salt and ground black pepper to taste
- 2 onions, minced
- 1 1/4 pounds ground beef
- 1 (11 ounce) can canned whole kernel corn (such as Green Giant Niblets®), drained
- 1 (14.75 ounce) can cream-style corn
- Preheat oven to 350 degrees F (175 degrees C).
- Place potatoes into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 20 minutes; drain.
- Mash potatoes with 2 tablespoons margarine; stir in milk. Season with salt and pepper.
- Heat 2 tablespoons margarine in a large skillet over medium heat; stir in onions and saute until onions are translucent, about 5 minutes. Spread onions evenly over bottom of a 9×13-inch baking dish.
- Cook and stir ground beef in same skillet over medium heat until no longer pink, breaking up large pieces, about 5 minutes. Layer beef into baking dish evenly over onion layer.
- Wipe out skillet; place corn and creamed corn in skillet over medium heat and cook and stir until bubbly, about 5 minutes. Pour corn mixture over beef in baking dish. Spread mashed potatoes over corn mixture; dot with remaining 4 tablespoons margarine. Sprinkle with salt and pepper.
- Bake in the preheated oven until casserole is bubbly and lightly browned at edges and margarine is melted, about 30 minutes.