Preheat the Oven: Preheat your oven to 180°C (fan).
Cook the Pasta: Bring a pan of salted water to the boil, add the penne pasta, and return to a boil. Reduce to a simmer for 10–12 minutes. Drain and set aside.
Sauté Aromatics: In a large pan, gently heat the olive oil and sauté the onion and garlic for about 4–5 minutes until softened.
Cook Chicken and Vegetables: Add the chopped chicken to the pan and cook, stirring, until no longer pink on the outside, about 5 minutes. Stir in the chopped red pepper and halloumi, cooking for another 5 minutes until the chicken is cooked through. Remove the pan from heat.
Make the Sauce: In a medium saucepan, combine the milk and flour. Bring to a boil, then reduce to a simmer, whisking thoroughly until smooth and thickened. Stir in the passata and chili flakes, simmering for about 5 minutes until the sauce thickens. Season to taste.
Combine Ingredients: Add the drained pasta and sauce to the large pan with the chicken and halloumi. Mix well.
Bake: Pour the mixture into an ovenproof dish, sprinkle with grated cheddar cheese, and place it in the middle shelf of the oven. Bake for 10–15 minutes until the cheese has browned slightly and is bubbling.
Serve this delicious pasta bake warm, and watch it become a household favorite!