Preheat your oven to 350°F (175°C).

In a large skillet over medium heat, cook the ground beef until browned, about 7-10 minutes. Drain excess fat.

Add the chopped onion to the skillet and sauté for about 5 minutes until tender.

In a mixing bowl, combine the cream of mushroom soup, cream of chicken soup, sour cream, garlic powder, salt, and black pepper.

Fold in the cooked beef and sautéed onions, and add frozen mixed vegetables if desired.

Transfer the mixture into a greased 9×13-inch baking dish.

Sprinkle shredded cheddar cheese over the beef mixture.

Arrange a layer of frozen tater tots on top, covering the cheese.

Bake for 30-40 minutes until tater tots are golden and cheese is bubbly.

Allow the casserole to cool for a few minutes before serving.