This healthy shepherd's pie is topped with a deliciously crunchy sweet potato, parsnip and parsley rosti. With melt-in-the-mouth lamb coated in a rich tomato sauce, this hearty family favourite is perfect on chilly nights.
Preheat the oven to gas 6, 200°C, fan 180°C. Cut half the parsnips and all the leeks, sweet potato and carrots into generous, bite-sized pieces. Toss with 1 tbsp olive oil and spread out on a baking tray. Roast for 20-25 minutes until just beginning to brown.
Meanwhile, put 1 tbsp of olive oil in a deep frying pan and set over a high heat. Add the lamb and brown on all sides then remove to a plate and reduce the heat to low-medium. Add the chopped onion to the pan and cook gently for 10 minutes, stirring often. Return the lamb with the garlic and tomato purée, cooking gently for a minute or so.
Combine the cornflour with 3 tbsp of the stock in a cup to make a paste. Whisk this into the remaining stock then turn the heat up slightly and add to the lamb mixture, stirring often to prevent lumps forming. Bring to the boil, partially cover and simmer gently for about 15 minutes, until thickened. Stir in half the parsley then remove from the heat and stir in the roast vegetables. Spoon this filling into a medium-sized ovenproof dish (about 20cm x 30cm). Reduce the oven temperature to gas 4, 180°C, fan 160°C.
While the lamb mixture simmers, coarsely grate the remaining parsnips. Grate the potato separately and wring out in a clean tea towel, to remove as much liquid as possible. Toss the dried-out potatoes and parsnips together with the remaining 1 1/2 tablespoons of olive oil and remaining parsley. Add a good seasoning of salt and pepper.
Arrange this rosti mixture on top of the filling in an even layer. Bake for about 40 minutes, until well-browned and tender on top and bubbling beneath. Rest for 5 minutes before serving with steamed green vegetables.
Freezing and defrosting guidelines
Cook as instructed and allow to cool completely. Then transfer to an airtight, freezer-safe container, seal freeze for up to 1-3 months. To serve, defrost thoroughly in the fridge overnight before reheating. To reheat and serve, place on medium heat, stirring occasionally until the dish is heated through.
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