Cauliflower, leek and cheese gratin

Method

1. 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 and cheese. Season well with salt and pepper.
2. Meanwhile cook the leek and cauliflower in a pan of boiling salted water for 4-5 minutes until just tender. Drain well.
3. Spoon the leek and cauliflower into a serving dish, pour over the cheese sauce, mix and scatter with thyme. Bake for 30 minutes until bubbling and golden.