Brown the ground beef in a large pot over medium-high heat, breaking it into small pieces. Cook for 2 minutes, then add the diced onion. Continue cooking for 5 minutes, or until the beef is fully browned and the onion is tender. Drain excess fat.

Stir in the garlic and diced bell pepper, cooking until the peppers are softened, about 4 minutes. Mix in the chili seasoning and tomato paste, cooking for an additional minute.

Pour in the tomato sauce, diced tomatoes (including their juices), and chicken broth. Combine thoroughly and bring the mixture to a boil. Lower the heat to maintain a gentle simmer. Cover partially and let it cook, allowing the flavors to meld and thicken. Add kidney beans during the last 10 minutes of simmering.

Preheat the oven to 400°F.

In a large pot, bring salted water to a boil and cook the macaroni until just al dente, following package instructions. Drain and set aside.

In a Dutch oven or large saucepan, melt the butter over medium heat until it starts to foam. Whisk in the flour and stir constantly for 2 minutes. Gradually pour in the heavy cream, whisking continuously, followed by the milk in small increments.

Bring the mixture to a gentle boil, then reduce the heat to a simmer. Stir in the mustard powder, onion powder, hot sauce, salt, and pepper. Lower the heat to the minimum setting and gradually incorporate the shredded cheese, stirring until fully melted and smooth.

Combine the cooked macaroni with the cheese sauce, stirring gently. For a creamier texture, reduce the amount of pasta slightly as the noodles absorb the sauce over time.

Gently fold the prepared chili into the macaroni and cheese. Adjust the ratio of chili to macaroni to your preference, using all or part of the chili. Excess chili can be stored or frozen for later use.

Transfer the mixture to a baking dish, topping it with 1 ½ cups of shredded cheddar cheese. Bake uncovered for 5 minutes, or until the cheese is fully melted.

Garnish with fresh parsley before serving.