I start by browning ground beef with diced onion over medium-high heat for a few minutes until the meat is no longer pink and onions are softened. Then I drain off excess fat. I add diced bell pepper and garlic, cooking until softened. Next, I stir in the chili seasoning mix and tomato paste for about a minute so the spices bloom. After that I pour in tomato sauce, undrained diced tomatoes, and broth, bring it to a boil, then reduce to a simmer; while simmering I partially cover the pot and add kidney beans in the last 10 minutes.
While the chili is simmering, I cook pasta in salted boiling water until just al dente so it won’t fall apart later. I melt butter in a pot, whisk in flour and cook the roux for about 2 minutes. Then I add cream and milk gradually, stir in mustard powder, onion powder, salt, pepper, and hot sauce. Once it’s smooth, I fold in the freshly shredded cheddar cheese until everything is melted and silky. Finally I stir the pasta in.
Next I gently stir the chili into the mac & cheese (or vice versa) using a silicone spatula—how much chili you add is up to your preference. I pour into a baking dish if not already in an oven-proof pot. Then I top with extra shredded cheddar and bake in a 400 °F oven for about 5 minutes until the cheese is melted and just starting to golden. Garnish with fresh parsley.