Begin by heating the butter in a Dutch oven or a large pot over high heat. Once hot, add the stew meat, searing it until the edges are brown—make sure to turn the meat to brown all sides.

Next, add the diced onion to the pot. While the beef continues to sear, sauté the onions, stirring continuously to prevent sticking. Cook for about three minutes until the onions are soft and translucent.

Add mixed vegetables, cubed potatoes, canned diced tomatoes (with their juice), beef broth, bouillon cube, Worcestershire sauce, and bay leaves.

Bring to a boil then reduce to a simmer. Cover the pot and let it simmer for at least two hours, or until the potatoes are tender and the meat reaches your desired tenderness.

Before serving, taste the soup and add salt and pepper as needed. Remove the bay leaves.