Pre-heat oven to 180C Fan.
Bring a pan of salted water to the boil, stir in the pasta and return to the boil. Turn down to simmer for 8 minutes. Then drain and set aside.
Whilst the pasta is cooking, in a large pan, heat the chorizo to release its fat for about 4 - 5 minutes then remove the chorizo with a slotted spoon. Leave the fat and juices in the pot.
Add the chicken and cook in the chorizo juices stirring until no longer pink, about 5 minutes. Stir in the red pepper and cook for 5 minutes until the chicken is cooked through. Stir Chorizo back in and then remove from pan from the heat.
Add the milk and flour into a medium sized saucepan. Bring the mixture to the boil, then turn it down to simmer and whisk it thoroughly until you have a smooth and thickened white sauce. Then stir in the passata and chilli flakes. Simmer for about 5 minutes until the sauce has thickened. Season to taste.
Add drained pasta and sauce to the large pan containing the chicken and chorizo and mix well.
Pour the contents of the large pan into an oven proof dish, sprinkle with the cheese and place onto the middle shelf of your oven.
Bake for 10 - 15 minutes until the cheese has browned slightly and is bubbling.
Once cooked, serve with chopped basil sprinkled on top.