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. Set aside.
Whilst the pasta is cooking, in a large non-stick pan, heat 1 tablespoon of the olive oil, add the chicken and cook until chicken is no longer pink inside, about 8 minutes. Use a slotted spoon to remove chicken to a casserole dish.
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 cream cheese. Simmer for about 5 minutes until the sauce is thickened and creamy. Season to taste.
Drain pasta, add to the casserole dish with the sauce and mix well. Sprinkle with the cheddar cheese, mozzarella and parsley and place onto the middle shelf of your oven.
Bake for 10 - 15 minutes until the cheese has browned slightly and is bubbling.