Instructions:

Prepare the Beef Mixture:

Preheat oven to 375°F (190°C).
In a large skillet, brown the ground beef over medium-high heat, breaking it apart with a spoon as it cooks. Drain any excess grease.
Add the chopped onion and minced garlic (if using) and cook until softened, about 5 minutes.
Stir in the condensed soup and milk/sour cream until smooth.
Stir in half of the shredded cheddar cheese. Season with salt and pepper to taste.
Assemble the Casserole:

Pour the beef mixture into a greased 9×13 inch baking dish.
Arrange the frozen tater tots in a single layer over the beef mixture.
Bake:

Bake for 30-40 minutes, or until the tater tots are golden brown and the cheese is melted and bubbly.