Heat the olive oil in a skillet over medium heat. Add the ground beef and cook until browned, about 5-7 minutes. Drain any excess fat.
Add the diced onion and minced garlic to the skillet, cooking until the onion is translucent and fragrant, about 3 minutes.
Transfer the beef mixture to your slow cooker. Stir in the taco seasoning, diced tomatoes with green chilies, tomato sauce, and chicken broth.
Cover and cook on low for 4 hours, allowing the flavors to meld beautifully.
After 4 hours, stir in the uncooked pasta shells. Cover again and cook on high for an additional 30-45 minutes, until the pasta is tender.
Once the pasta is cooked, stir in the shredded cheddar cheese and sour cream until the cheese is melted and the sauce is creamy. Season with salt and pepper to taste.
Serve hot, garnished with your choice of cilantro, jalapeños, or avocado for an extra burst of flavor.
