Warm a large, deep skillet over medium-high heat and add olive oil. Introduce the ground beef, using a spatula to break it into small crumbles. Add the chopped onion and minced garlic, cooking until the onions turn translucent and take on a golden hue.
Stir in the sliced mushrooms and continue sautéing for approximately 5 minutes, allowing them to soften. Let any excess moisture evaporate fully.
Incorporate the flour, mixing thoroughly until no dry spots or lumps remain.
Pour in the beef broth and heavy whipping cream, then add Worcestershire sauce, salt, and pepper. Bring the mixture to a gentle simmer. Reduce the heat to low and continue to cook for about 5 minutes, allowing the flavors to meld.
Take the pan off the heat and fold in the sour cream, mixing until well combined. Adjust seasoning if needed. Serve hot atop pasta, rice, or potatoes.