Heat oven to 180C/160C fan/gas 4. Put the broccoli in a casserole dish, add 1 tbsp water and roast in the oven for 10 mins while you make the sauce.

Melt the butter in a small pan over a medium heat, add the flour and cook until it bubbles and thickens, take off the heat and whisk in a big splash of the milk. Return to the heat and slowly add the rest of the milk. Stir in the mustard and cheese and season well.

Remove the broccoli from the oven, add the chunks of toast to the dish, mixing them up with the broccoli. Pour the cheese sauce over. Grate the parmesan over the top and put back in the oven for 10 mins, turning on the grill for the last 3 mins, until the top is golden and the dish is bubbling. Leave to sit for 5 mins before serving.