In a large Dutch oven over medium-high heat, cook ground beef and diced onion until beef is browned and cooked through, about 6-8 minutes. Drain excess grease, leaving about 1 tablespoon.
Add bell pepper and garlic to the pot. Cook for 2 minutes until softened. Stir in chili seasoning and tomato paste, cooking for 1 minute.
Add tomato sauce, diced tomatoes with juice, and broth. Bring to a boil, then reduce to low and simmer for 30 minutes. Stir in kidney beans during the last 10 minutes.
Meanwhile, cook macaroni according to package directions until al dente. Drain thoroughly and set aside.
In a large saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute. Gradually whisk in heavy cream and milk until smooth.
Bring sauce to a boil, then reduce to simmer. Add mustard powder, onion powder, salt, pepper, and hot sauce. Remove from heat and stir in 1 1/2 cups cheddar cheese until melted. Add drained macaroni and toss to coat.
Preheat oven to 400°F. Combine chili and mac and cheese in the larger pot, stirring gently. Transfer to an oven-safe dish if needed.
Sprinkle remaining 1 1/2 cups cheddar cheese on top. Bake for 5 minutes until cheese is melted and bubbly. Garnish with fresh parsley and serve.
