Hi I use britmums aubergine lasagne topping. It's 28g of Parmesan, 250ml milk, tablespoon of cornflour, 42g mozarella. Heat milk in a pan, mix cornflour with a little water and add to milk. Whisk until starts to thicken, then add 28g Parmesan. Season with salt and pepper, pour over lasagne and top with mozzarella. Bake until golden. It's lovely.