Heat a large skillet over medium heat. Add the garlic and onion and sauté until fragrant and soft, about 3 to 4 minutes.
Next, add the lean ground beef to the skillet. Cook until browned, about 3 to 5 minutes, crumbling as you cook.
Once the beef is cooked, drain any excess fat from the skillet.
Add the cooked beef mixture to a large pot. Pour in the chicken broth, diced tomatoes, both types of beans, chili powder, and brown sugar. Season with salt and pepper.
Bring the pot to a simmer. Stir everything together and allow to bubble gently.
Add the elbow macaroni. Stir it in and return the pot to a boil. Cover, reduce heat, and simmer until pasta is cooked, about 13 to 15 minutes.
Check the pasta for doneness. If necessary, let it simmer a few more minutes.
Remove the pot from heat. Stir in the shredded cheese until melted and well combined.
Serve immediately while hot. Top with sour cream and green onions.
