In a large skillet, heat olive oil over medium heat. Add the diced onions and minced garlic, sautéing until the onions are translucent.

Add the ground beef to the skillet, breaking it apart with a spatula. Cook until browned and fully cooked through.

Add the sliced mushrooms to the skillet and cook until they are tender, about 5 minutes.

Sprinkle the flour over the mixture and stir well to combine. Cook for an additional minute.

Gradually pour in the beef broth, stirring constantly to prevent lumps from forming. Bring to a simmer and cook for about 5 minutes until the sauce thickens.

Lower the heat and stir in the sour cream, mixing until well combined. Season with salt and pepper to taste.

Serve the stroganoff over cooked egg noodles, mashed potatoes, or rice. Garnish with fresh parsley if desired.