Cook the pasta according to the pack instructions and drain.
Meanwhile, combine the cornflour and mustard with 3tbsp of the milk in a saucepan. Pour in the remaining milk, mix well and bring to the boil. Add the cheese and cook for a minute or two until thickened and cheese melted1.
Mix all the ingredients and transfer to an oven proof dish. Bake for 20–25 min and serve with salad.
For a crunchy topping mix 25 g grated cheese with 100g wholemeal breadcrumbs and scatter on the top before baking in the oven.