Preheat the oven

• Preheat the oven to 190 °C.

Brown the beef

• Heat the oil in a frying pan over medium heat.
• Add the onion and cook until softened.
• Add the ground beef and cook until browned, then season with salt and pepper.

Make the filling

• Stir the cream of mushroom soup and milk into the beef mixture until combined.

Assemble the casserole

• Spread the beef mixture in the baking dish.
• Top with the frozen tater tots in an even layer.
• Sprinkle the cheddar cheese over the top.

Bake

• Bake until the tater tots are golden and the cheese is melted and bubbling.

Rest and serve

• Let the casserole rest before serving.