Heat a large skillet over medium heat. Add the ground beef and cook until browned, breaking it apart with a spatula. Add the chopped onion and minced garlic, and cook until softened, about 3–4 minutes. Drain any excess grease.
Mix the base:
In a mixing bowl, combine the cooked ground beef, cream of mushroom soup, cream of chicken soup, sour cream, and shredded cheese. Stir until well mixed. Season with salt and pepper to taste.
Assemble the casserole:
Spread the meat mixture evenly across the bottom of the 9x13-inch baking dish. If using frozen peas and carrots, layer them over the meat mixture. Arrange the tater tots in a single layer on top.
Bake:
Place the casserole in the preheated oven and bake for 35–40 minutes, or until the tater tots are golden and crispy.
Add cheese (optional):
If you love extra cheese, sprinkle additional shredded cheddar over the casserole during the last 5 minutes of baking.
Serve:
Remove the casserole from the oven and let it cool slightly. Garnish with chopped parsley or green onions, if desired.
Notes
If you're a vegetarian, substitute the ground beef with a plant-based alternative or extra veggies like mushrooms and zucchini.