In a large skillet over medium-high heat, brown the ground beef with the diced onion and minced garlic. Cook until the beef is no longer pink, about 5-7 minutes. Then, drain any excess grease from the pan.

In the same skillet, melt the butter over medium heat. Add the flour and whisk until it combines with the butter, forming a smooth roux.

Gradually pour in the beef broth while whisking. Bring the mixture to a boil, cooking for about 2-3 minutes until it thickens.

Reduce the heat to medium. Add the sour cream and cream of mushroom soup, whisking until everything is well combined.

Return the cooked ground beef mixture back to the skillet. Season with salt and pepper to taste. Let it simmer for about 5 minutes before serving.