Preheat the oven to 180°C.
Cook the gluten free pasta until just al dente. Strain and set aside.
Heat a non stick pan to a medium/high heat. Once hot, add 1 tbsp rapeseed oil.
Add the chicken and cook for 2-3 minutes to seal.
Add the onion and the broccoli and continue to cook for a further 3-4 minutes until the onion is beginning to soften.
Season with salt and pepper. Add the milk and cream and cook for a further 4-5 minutes until the liquid has started to reduce.
Mix the gluten free flour with the water in a small bowl to form a paste. Add to the pan and cook, stirring continuously, for a further 2-3 minutes until the sauce starts to thicken.
Add the strained pasta to the pan. Stir until coated in sauce.
Transfer to an ovenproof dish. Sprinkle with gluten free breadcrumbs and grated cheddar. Bake in the preheated oven for 15-20 minutes until golden and bubbling.