1. Brazen the cubed sirloin meat with the butter, onion, and garlic on medium heat in a large pot. After the meat is browned, add 2 cups of water. Let sit for 5 minutes, as this will be the beginning of the broth.
2. Add in cubed potatoes, carrots, celery, tomatoes, mushrooms, McCormicks beef stew mix, beef bouillon (optional), thyme and about 6 cups of water. Bring to a boil.
3. Add 2 tbsp cornstarch mixed with 1/2 cup of water to thicken.
4. Continue cooking until potatoes are soft to touch. Consider serving homemade bread to soak in the goodness!