Prepare 400g broccoli (one head) by removing the stalk and cutting off the florets. Cut any large florets in half so that they are all a similar size

Bring a large pan of water to the boil and add 1 tsp table salt before adding the prepared broccoli

Cook the broccoli for 5-6 minutes until you can just insert a knife into the stem. You don't want the florets to be fully cooked at this point

Drain the broccoli and allow to steam dry thoroughly

Mix together 80g extra mature cheddar cheese, 25g Parmesan and 25g mozzarella and set aside

Preheat your oven to 180°C (fan assisted, 200°C non fan assisted)

In the pan you cooked the broccoli in, melt 20g butter over a low heat

Once melted add 2 tbsp plain flour and stir until a paste forms. Cook for 2 minutes

Gradually add 300ml of semi skimmed milk. Start by adding just a splash and stir until it is completely absorbed and only then add another splash. Don't be tempted to add a lot at a time

Once you have added all of the milk, add in 3/4 of the cheese, a small handful at a time

Stir until all of the cheese is melted and then add ¼ tsp mustard powder, ¼ tsp white pepper and 1 tsp sea salt. Stir well

Add the broccoli to the cheese sauce and carefully stir making sure all of the broccoli is coated in the sauce

Tip the broccoli into an oven proof dish

Scatter over the reserved cheese

Cook for 20-25 minutes or until the cheese on top is your desired shade of brown