Fat Boy Tater Tot® Casserole

cooking spray
1 (32 ounce) package frozen bite-size potato nuggets (such as Tater Tots®), divided
1 pound ground beef
1 cup chopped onion
2 teaspoons Worcestershire sauce
2 teaspoons Fat Boy Steak Rub
1 teaspoon garlic powder
1/2 teaspoon ground black pepper
1 (10.75 ounce) can condensed cream of mushroom soup
1/2 cup milk
1/2 cup grated Cheddar cheese
1 teaspoon Worcestershire sauce
1 cup grated Cheddar cheese

Preheat oven to 425 degrees F (175 degrees C). Prepare a 13×9-inch casserole dish with cooking spray. Spread 20 Tater Tots® in the casserole dish. Bake in preheated oven until warmed through, about 10 minutes. Heat a large skillet over medium-high heat. Cook and stir beef and onion in the hot skillet until beef is completely browned, 5 to 7 minutes; drain and discard grease. Season beef mixture with 2 teaspoons Worcestershire sauce, steak seasoning, garlic powder, and black pepper. Stir cream of mushroom soup, milk, 1/2 cup Cheddar cheese, and 1 teaspoon Worcestershire sauce together in a bowl. Smash the warmed Tater Tots® in the casserole dish to cover the bottom completely. Spread ground beef mixture over the mashed Tater Tots®. Pour soup mixture evenly over the beef layer. Top with remaining Tater Tots® and sprinkle 1 cup Cheddar cheese evenly over the Tater Tots®. Bake in preheated oven until casserole is bubbly and potatoes golden brown, 25 to 35 minutes.