Preheat the oven to 180. Discard the outer leaves of the cauliflower and break in half or quarters, depending how big the pan is. In a large saucepan of boiling water, blanch the cauliflower for 3 minutes, remove and leave to cool. Meanwhile, in a medium saucepan, melt the butter on a medium heat. Add the flour, and using a wooden spoon, mix well the mixture starts to turn golden. Turn the heat down and gradually adding the milk, whisking continually. Add the mustard and paprika and cook for a couple more minutes or until the sauce has thickened. Add all the cheddar except 2 tablespoons and all the parmesan except 1 tablespoon. Season to taste.
Break the cauliflower into florets, and place in a suitable ovenproof dish. Pour over the sauce, mixing if needed to ensure all the cauliflower is covered. Break in the taleggio in chunks and sprinkle over the other remaining cheeses. bake for 30 minutes until golden and bubbling.