Preheat oven to 400 degrees
Prepare mashed potatoes.
Heat 1 tablespoon of oil in skillet. Then brown ground beef on medium heat. This will take around 5 minutes. Drain excess oil.
Add tomato soup, frozen mixed veggies, and 1/2 cup of water to the beef. Allow to cook on low heat for 5-10 minutes.
Spread the ground beef and vegetable mixture onto the bottom of a greased 9x13 baking dish. Make sure it's even! Then add mashed potatoes over top. Finally add a layer of cheese.
Cook on center rack for 30 minutes. The cheese will begin to brown.