Preheat your oven to 350°F and lightly butter a 9x13 baking dish. This prevents sticking and adds subtle richness to the bottom layer.
Brown the ground beef in a large skillet over medium-high heat, breaking it into small crumbles as it cooks. Add diced onion and garlic, cooking for 3 minutes until fragrant, then drain excess fat using a colander.
Stir the cream of mushroom soup, beef broth, Worcestershire sauce, and sour cream into the cooked beef mixture. Season generously with salt, pepper, garlic powder, and onion powder, then fold in frozen mixed vegetables until evenly distributed.
Spread this hearty beef tater tot casserole crowd-pleasing mixture into your prepared baking dish, pressing gently to create an even layer. Sprinkle 1 cup of shredded cheddar cheese over the beef layer, distributing it uniformly across the surface.
Arrange frozen tater tots in a single layer over the cheese, covering the entire surface. Bake for 30 minutes until tots begin turning golden brown at the edges.
Remove the casserole from the oven and carefully top with remaining cheddar cheese. Return to oven for 5 minutes until cheese melts completely and tater tot tops reach deep golden-brown perfection.
Let it rest for 5 minutes before serving, allowing the layers to set slightly and making portioning easier.