Lamb, harissa & cauliflower shepherd's pie

Method

• step 1

  Heat the oil in a large, deep, flameproof casserole dish over a medium-high heat. Roughly roll the lamb mince into meatballs and fry until browned and caramelised all over. Remove to a bowl using a slotted spoon.

• step 2

  Meanwhile, separate the leaves from the cauliflower and cut the florets away from the stalk. Set aside, then finely chop the leaves and stalk. Tip the leaves and stalk into the casserole along with the onions, celery, carrots and bay leaves, and reduce the heat to medium. Stir in a large pinch of salt, partially cover and cook for 15-20 mins until starting to soften. Mix in the garlic and spices, then uncover and cook for a few more minutes until fragrant.

• step 3

  Mix in the tomato purée, stirring to coat, and cook for 5 mins more, stirring often until darkened and caramelised. Return the meatballs to the dish, breaking them up as you stir, pour in the stock and mix in the harissa. Bring to a simmer and bubble gently for 1 hr until tender.

• step 4

  Meanwhile, for the mash, tip the cauliflower florets and potatoes into a saucepan. Cover with cold water and add a generous pinch of salt. Bring to the boil and cook for 12-15 mins until everything is tender. Drain well and leave to steam-dry for 5 mins. Put the butter and milk in the pan and set over a low heat until the butter has melted. Return the potatoes and cauliflower to the pan and mash well. Mix in the egg yolk, if using, and chopped parsley, and season to taste.

• step 5

  Mix the peas into the lamb ragu, stirring well, then season to taste. Tip the mixture into a deep baking dish, then spoon the mash into a piping bag fitted with a wide round or fluted nozzle and pipe it over the filling, working from the outside in. Or, spoon some of the mash around the edge to enclose the filling, then spoon the rest into the middle. Scrape a fork over the mash to create ridges, if you like, and season. Will keep chilled for up to two days or frozen for three months. Defrost in the fridge overnight before cooking.

• step 6

  Heat the oven to 200C/180C fan/gas 6 and bake for 30-35 mins (or 45-50 mins from chilled) until golden brown all over, bubbling and piping hot.