In a large skillet, add a tablespoon of oil and sauté onions, peppers, and garlic until soft. Remove the sautéed veggies and set aside.
Add the ground beef and brown over medium-high heat. Season with chili powder and cumin. Add marinara sauce, diced tomatoes and kidney beans to the sautéed onions and beef mixture.
In a large sauce pan, add 1 cup of milk and heat over medium heat. Add 1 tablespoon butter, then add the chopped Cooper Cheese and stir until cheese is blended with milk. Add the cooked macaroni noodles.
Reduce heat to medium-low, then add the chili and stir until well mixed.
Serve in large bowls and garnish with sour cream and chopped green onions.