In a large pot or Dutch oven, heat a drizzle of oil over medium heat. Add ground beef and cook, breaking it apart, until no pink remains and browned, about 5-7 minutes. Stir in ground cumin, dried minced onion, and garlic powder during the last minute of cooking.

Once the beef is cooked, drain any excess fat and return the pot to heat. Stir in tomato paste, diced tomatoes with green chilies, beef broth, and whole milk. Mix together and bring to a gentle boil, allowing flavors to meld for about 2-3 minutes.

Add shell pasta to the boiling mixture, stirring well to ensure it is fully submerged. Reduce heat to medium-low and cover the pot, simmering for 10-12 minutes or until the pasta is al dente, stirring occasionally.

Once the pasta is cooked, lower heat and stir in remaining milk, Monterey Jack cheese, and mild cheddar cheese. Stir until the cheese melts completely and creates a creamy sauce, about 2-3 minutes.

Serve the One Pot Cheesy Taco Pasta warm, spooning generous portions into bowls. Optionally, garnish with taco toppings like diced avocado, sour cream, or fresh cilantro.