Nutrition: Per serving
Heat 1 tbsp of the oil in a shallow, round flameproof casserole dish or ovenproof pan (ours was 23 cm) over a medium heat. Add the leeks and cook for 5 mins, stirring, until starting to soften. Add the kale or cabbage and cook for another 5 mins until wilted.
Heat the oven to 200C/180C/gas 6. Tip in the butter beans, peas, stock, crème fraîche, pesto and the lemon juice and zest. Stir to combine, simmer for 3 mins and season well. Scrunch up the filo sheets and put them on top of the pie filling, brush over the remaining oil and sprinkle with nigella seeds, if using. Bake for 25-30 mins until golden brown.
