Put the broccoli in a pan of boiling water and simmer for 5 minutes. Drain and put in a large baking dish.
2 head broccoli
Make the cheese sauce by putting the milk, flour and butter in a sauce pan on a gentle heat. Whisk as the butter melts and the sauce starts to thicken. This will take 3-4 minutes. Add the cheese and mustard and whisk until melted.
500 ml whole milk, 4 tablespoon plain flour, 50 g butter, 100 g cheddar, 1 teaspoon English mustard
Pour the cheese sauce on the broccoli and mix well. Put in a preheated oven at 190°C/375°F/Gas 5 for 30 minutes.
You can use dijon, wholegrain or English mustard in the cheese sauce, or just leave it out.
Add a crispy topping to this side, by sprinkling it with Parmesan before putting it in the oven.
You could even mix some panko breadcrumbs in to the parmesan before sprinkling on top, to make it really crispy.