Preheat oven to 180C Fan.
Cook the pasta in boiling salted water, as per packet instructions, drain, stir in the frozen sweetcorn and set aside.
Whilst the pasta is cooking spray the bottom of a large frying pan about 5 times with the cooking spray. Turn the heat on high and then turn it down to medium when the oil starts to bubble.
Add the onion and sauté for 2- 3 minutes then add the garlic and sauté for a further minute. Be careful not to burn the garlic. Stir in the chicken chunks and cook, stirring until the outsides are no longer white. Set aside.
Pour the milk and corn flour mixture into a medium sized saucepan. Bring the mixture to the boil, then turn it down to simmer whilst you stir it constantly with a wooden spoon to make a white sauce.
Once the sauce has thickened add 25g of the grated cheese and stir it in until combined.
Pour the pasta and sweetcorn into a large casserole dish and then add the chicken onion mixture. Add the sauce to this mixture and stir everything well until well coated by the sauce.
Sprinkle the rest of the grated cheese over the top and bake in the oven for 15-20 minutes until the cheese has browned slightly and is bubbling.
Serve with a simple side salad or simple green vegetables like peas and / or broccoli.