To make the sauce, pour the milk into a pan with the butter, bay leaves and cornflour, and heat gently, stirring all the time, until it thickens into a smooth, creamy sauce. Remove the bay leaves, add 100g of the cheese and season to taste. Pour over the cauliflower and scatter with the remaining cheese. If cooking now, go straight to step 3; alternatively, cover and chill. Can be made a day ahead.