Using a steamer, place the cauliflower over the different levels evenly and steam on high for 15 minutes. Place the cauliflower into a 3 litre, oven safe bowl.
Using a 3 litre pot, melt the butter and then add the flour. Stir over a low heat for 3 minutes. Add the milk 1 cup at a time until all milk has been added and the white sauce is lump free. Stir using a whisk for 15 minutes or until the sauce is thick and creamy. Add the tasty cheese and stir until melted through.
Pour over the cauliflower and top with parmesan cheese. Place into the oven for 25 minutes.
