Start by warming the olive oil in your pot over medium heat. You will know it is ready when it shimmers just a bit. This step adds richness and depth to the dish, so do not skip it.
Add the diced onion and garlic to the pot, stirring them for about 3-5 minutes until they are soft and fragrant. Keep an eye on them to avoid burning.
Toss the ground beef into the pot, breaking it apart as it cooks. This should take about 5-7 minutes until it is well-browned and no longer pink.
Sprinkle the taco seasoning over the cooked beef, stirring to coat it evenly.
Pour in the diced tomatoes and green chiles, juices included. Mix everything well.
Stir in the uncooked pasta shells along with the beef broth. Ensure the pasta is fully submerged.
Cover the pot and let it simmer for about 15-20 minutes. Stir occasionally while keeping the lid on to retain steam.
Once the pasta is cooked, remove the pot from heat and stir in the shredded cheddar cheese until it melts smoothly.
Top with sliced green onions before serving. Serve hot and enjoy this hearty meal.