Prepare the beef mixture:
In a large skillet, cook the ground beef and chopped onion over medium heat until browned. Drain excess fat. Add ketchup, mustard, Worcestershire sauce, garlic powder, onion powder, salt, and pepper. Stir to combine and cook for 2-3 minutes.

Make the creamy sauce:
In a medium bowl, whisk together the cream of mushroom soup and milk until smooth. If you prefer a creamier sauce, you can add more milk, but it should be thick.

Assemble the casserole:
Preheat your oven to 375°F (190°C). In a 9×13-inch casserole dish, spread the beef mixture evenly across the bottom. Pour the soup mixture over the beef and spread evenly. Top with shredded cheese and carefully arrange the tater tots in a single layer over the cheese.

Bake the casserole:
Bake for 30-35 minutes, or until the tater tots are golden brown and crispy. For extra crispiness, you can bake for an additional 5-10 minutes, watching to ensure they don’t burn.

Serve:
Let the casserole cool for a few minutes before slicing into squares and serving hot. Optional: Garnish with chopped green onions, pickles, or extra ketchup and mustard for added flavor.