Preheat your oven to 375°F (190°C).

In a large skillet, heat the olive oil over medium-high heat. Add the ground beef and chopped onion. Cook, breaking up the beef with a spoon, until the beef is browned and the onion is softened, about 8-10 minutes. Drain any excess grease from the skillet.

To the browned beef and onion mixture, add the condensed cream of mushroom soup, milk, ketchup, yellow mustard, and Worcestershire sauce. Stir well to combine all ingredients thoroughly. Season with salt and black pepper to taste. Continue to cook over medium heat, stirring occasionally, until the mixture is heated through and slightly simmering.

Pour the beef and sauce mixture evenly into a 9x13 inch baking dish. Sprinkle 1 cup of the shredded cheddar cheese over the beef mixture. Arrange the frozen tater tots in a single layer over the cheese.

Place the baking dish in the preheated oven. Bake for 25-30 minutes, or until the tater tots are golden brown and crispy. The sauce underneath should be bubbly.

Remove the casserole from the oven. Sprinkle the remaining 1 cup of shredded cheddar cheese over the crispy tater tots. Return the casserole to the oven and bake for an additional 5-10 minutes, or until the cheese is melted and bubbly.

Once baked, remove the casserole from the oven and let it rest for 5-10 minutes before serving. Serve hot and enjoy!