Prepare Ingredients - Set your Greek yogurt/sour cream and frozen vegetables on the counter. The dairy will combine with your hot soup better if it's not cold. Allow the frozen veggies to begin thawing a bit.
Cook Potatoes - Boil your potatoes in salted water until tender (about 20 minutes), then drain all the liquid. Remove about half of your cooked potatoes and set aside. Mash the remaining potatoes in the pot with the butter or ghee. Season lightly with sea salt and pepper to your taste.
Brown the Meat - Meanwhile, in a large stockpot or Dutch oven, add your ground meat of choice and cook, mincing it with a wooden spoon. Drain any excessive grease and season lightly with sea salt and ground pepper.
Add Aromatics - Stir in the diced onion, celery, garlic, and seasonings then cook while stirring for a few more minutes. This creates a flavorful base for your soup, allowing the vegetables to soften and the herbs to release their aromatic oils.
Incorporate Vegetables and Broth - Add the frozen vegetables and stir well to combine. Pour in your bone broth and bring everything to a boil, then reduce to low and simmer for 10 minutes to allow the flavors to meld together.
Add Potatoes - Stir in both the mashed potatoes and the remaining un-mashed potatoes and simmer for about 5 minutes. The mashed potatoes will help thicken the soup while the potato chunks provide texture similar to a traditional shepherd's pie.
Finish with Dairy - Add your Greek yogurt or sour cream and stir until combined, then remove the pot from heat. The dairy adds creaminess and a slight tanginess that balances the rich flavors of the soup.
Garnish and Serve - Ladle into bowls and garnish with freshly cracked pepper, parsley, green onions, and a sprinkle of cheddar cheese if desired.