01 - Preheat oven to 400°F. Lightly grease a 9x13-inch baking dish.
02 - In a large skillet over medium-high heat, cook ground beef, breaking it up with a spoon, until browned and fully cooked, about 5 to 7 minutes. Drain excess fat.
03 - Add diced onion and minced garlic to the beef in the skillet. Sauté for 2 to 3 minutes, stirring occasionally, until onion softens and becomes fragrant.
04 - Stir in condensed cream of mushroom soup, whole milk, Worcestershire sauce, dried thyme, salt, and black pepper. Mix thoroughly until heated through and combined.
05 - Reduce heat to low and fold in 1 1/2 cups of shredded cheddar cheese. Stir gently until cheese is melted and the mixture is smooth.
06 - Pour the prepared beef mixture into the greased baking dish and spread evenly.
07 - Evenly arrange frozen tater tots in a single layer over the beef mixture.
08 - Place the dish uncovered in the oven and bake for 30 minutes, or until the tater tots are crisp and golden.
09 - Sprinkle the remaining 1/2 cup cheddar cheese evenly over the tater tots. Return casserole to oven for 5 to 7 minutes until cheese is melted and bubbly.
10 - Allow casserole to stand for 5 minutes before portioning and serving.