In a skillet, cook the ground beef over medium heat until browned. Drain excess fat.
Add the chopped onion and minced garlic to the skillet. Cook until the onion is translucent.
Sprinkle the flour over the beef mixture and stir well to combine.
Gradually add the beef broth and milk, stirring constantly until the mixture thickens into a gravy. Season with salt and pepper to taste.
Transfer the beef gravy mixture to a baking dish. Spread the mashed potatoes evenly over the top.
Sprinkle the shredded cheddar cheese over the mashed potatoes.
Bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly.
Let the casserole cool for a few minutes before serving.
Notes:
This casserole is perfect for a cozy family dinner. You can also add vegetables like peas or carrots to the beef mixture for extra flavor and nutrition.