Preheat oven to 250C. Heat olive oil in a medium, oven-proof frying pan. Add most of the chopped leeks and saute for five minutes. Add the romanesco pieces and lemon zest and spoon the oily leeks over them. Transfer the pan to the oven and roast for 12-15 minutes or until soft. Prepare the sauce by pouring the cream into a small pan over a gentle heat. Add the wine, to taste. Add the remaining chopped leeks and mustard and heat gently for 3-4 minutes. Remove the romanesco from the oven and tip into a serving dish. Pour over the sauce, season and serve.
3 tbs olive oil
170g leeks, chopped
1 romanesco, quartered
1 lemon, zested
110ml double cream
2-3 tbsp white wine
1 tbsp wholegrain mustard
salt and freshly ground black pepper