Place the macaroni in a large pan of salted boiling water, then lower the heat, and partially cover with a lid. Simmer for 8-10 minutes, or according to the packet instructions – until ‘al dente’. The macaroni should be tender when you bite a piece, but not too soft. Drain the pasta and then return it to the pan – placing the lid on to keep it warm. Set aside, off the heat.
Now it's time to make the cheese sauce! Place the milk in a small saucepan, add the reduced-fat spread, and heat gently – until the reduced-fat spread has fully melted, and the mixture is steaming hot. Take care not to let the milk boil over.
In a small bowl, mix the cornflour with 3 tablespoons of water – until smooth. Then pour the cornflour mixture into the hot milk – stirring constantly with a balloon whisk or wooden spoon. Simmer for 3-5 minutes – all the while stirring constantly – until the mixture is smooth and slightly thickened. Stir in the grated cheese and mustard powder. Cover, and set aside.
Spray a frying pan with low-calorie cooking spray, and place over a medium heat. Add the chorizo and fry for 2 minutes. Then add the chicken and cook for a further 5 minutes – until the chicken is cooked through and lightly golden.
Add the garlic, smoked paprika, chilli powder, roasted red peppers, and spring onions, and continue to cook for a further 5 minutes – until the spring onions have softened.
Preheat the grill on a medium setting. Place the chicken and chorizo mixture and cheese sauce in the saucepan with the drained macaroni, and stir well.
Sprinkle the remaining cheese over the top, and place under the preheated grill for a few minutes – until the top is golden brown. Then scatter the chopped parsley on top, and serve with a mixed salad – or another accompaniment of your choice.