In a large pot or Dutch oven over medium-high heat, cook ground beef with diced onion, garlic powder, kosher salt, black pepper, Worcestershire sauce, and ground mustard. Stir occasionally and cook until the beef is no longer pink. Drain excess grease if needed.
Add diced potatoes, diced tomatoes with green chilis (including liquid), chicken broth, and whole milk to the pot. Stir well to combine.
Bring to a simmer over medium heat. Cook for about 15 minutes, or until the potatoes are fork-tender.
Reduce heat to low. Add cubed Velveeta cheese and sour cream. Stir until the cheese is melted and the soup is smooth.
In a small bowl, whisk together water and cornstarch until no lumps remain. Pour the slurry into the soup and stir well. Continue cooking for 3 to 5 minutes, or until the soup thickens slightly.
Serve hot, topped with crumbled bacon and pickles, if desired.