In a large cast-iron skillet over medium heat, add the ground beef and cook until browned, approximately 5 minutes. Use a wooden spoon to break it apart as it cooks for even browning. Once ready, remove the beef from the skillet, ensuring to reserve about 1 tablespoon of the flavorful fat left in the pan for the next steps.

In the same skillet with the reserved beef fat, add the diced onion and sauté over medium heat until translucent, roughly 3-4 minutes. Next, include the sliced mushrooms and continue to cook for about 2 more minutes until they are slightly caramelized and tender, filling your kitchen with a delicious aroma.

Stir in the trimmed green beans, minced garlic, and low-sodium broth into the skillet. Cook the mixture for about 2-3 minutes, allowing the green beans to become crisp-tender while absorbing all the savory flavors.

Once the green beans are ready, reduce the heat to medium-low. Add the room temperature cream cheese to the skillet, stirring until it fully melts and combines into the mixture. Gradually incorporate the full-fat sour cream until everything is well-blended into a creamy and luscious base.

Return the browned ground beef to the skillet, mixing it thoroughly with the creamy green bean mixture. Season generously with sea salt, freshly ground black pepper, Worcestershire sauce, and dried thyme. Stir everything together for about a minute until all ingredients are well coated and heated through.

Sprinkle the shredded Colby Jack cheese evenly over the entire casserole mixture in the skillet.

To melt the cheese, you can place the skillet under the broiler on high for 1-2 minutes or cover the skillet and cook on low heat for 3-4 minutes.