Cauliflower gratin

Method

1. Steam or boil the cauliflower florets for 6-8 minutes until very tender. Drain well.
2. Mix together the mascarpone, mustard and three-quarters of the cheese. Gently fold the cheesy mixture into the cooked, drained cauliflower (the heat of the cooked cauliflower will melt it slightly, making it easier to mix). Tip into a freezer-proof and ovenproof dish and scatter over the remaining Gruyère. Allow to cool completely. Wrap well with cling film, then freeze.
3. Allow the gratin to thaw completely. Preheat the oven to 200°C/fan180°C/gas 6. Remove the film and cover the dish with foil. Bake for 20 minutes, then remove the foil and cook for a further 15-20 minutes until golden brown and piping hot.