30g / 1oz butter
30g / 1oz plain flour
400ml / 13fl oz semi skimmed milk
3 tbsp double cream (optional)
150g / 5 ½ oz mature Cheddar, grated
1 leek, cut into chunks
Medium head of cauliflower, broken into equal-size florets
50g/2oz Panko breadcrumbs
Few thyme sprigs, leaves picked
Preheat the oven to 200°C/fan180°C/gas 6. Melt the butter in a wide-bottomed saucepan. When it foams, add the flour and stir for a minute. Gradually add the milk, stirring, until you have a smooth sauce. Bubble for 2 minutes, then remove from the heat and stir through the cream, if using, and 100g/3 ½ oz cheese. Season well.
Meanwhile cook the leek and cauliflower in a pan of boiling salted water for 4-5 minutes until just tender. Drain well.
Spoon the leek and cauliflower into a serving dish, pour over the cheese sauce, mix and scatter with thyme. Mix the remaining 50g/2oz cheese with the breadcrumbs and sprinkle over. Bake for 30 minutes until bubbling and golden.