Preheat the oven. Heat your oven to 400°F (200°C). Lightly grease a 9x13-inch baking dish.
Brown the beef. Heat oil in a large skillet over medium-high. Add the ground beef and cook, breaking it up, until no longer pink, about 5–7 minutes.
Drain excess fat if needed.
Sauté aromatics. Add the diced onion and cook until soft and translucent, about 3–4 minutes. Stir in the minced garlic and cook 30 seconds until fragrant.
Season the base. Stir in salt, pepper, Worcestershire sauce, and paprika. Taste and adjust seasoning to your preference.
Add veggies. Mix in the frozen vegetables and cook 2–3 minutes to take the chill off.
Make it creamy. Reduce heat to medium.
Stir in the cream of mushroom soup and milk until smooth and combined. Simmer 1–2 minutes to thicken slightly. Remove from heat.
Layer in the dish. Spread the beef mixture evenly in the prepared baking dish.
Sprinkle 1 cup of cheddar cheese over the top.
Add the tots. Arrange tater tots in a single, even layer on top. Keep them snug so they brown evenly.
Bake. Place on the center rack and bake 30–35 minutes, until the tots are golden and crisp and the filling is bubbling.
Finish with cheese. Sprinkle the remaining 1/2 cup cheddar over the tots and bake 5 more minutes, just until melted.
Rest and serve. Let the casserole rest 5–10 minutes to set. Garnish with chopped parsley or chives if you like.
Serve warm.