Toss the lamb with sea salt and plenty of black pepper.
Place in a shallow casserole pan on a high heat with 1 tablespoon of olive oil, turning until brown all over.
Meanwhile, peel the onions and carrots and chop into chunks the same size as the lamb.
Remove the lamb to a plate, leaving the fat behind in the pan.
Reduce to a medium heat, stir in the onions and carrots, tear in the sage leaves, and add a splash of water.
Cook for 10 minutes, stirring occasionally.
Put the lamb back in and stir in the pickle, then the flour.
Pour in the cider and 600ml of water to cover.
Preheat the oven to 180°C.
Place one potato on a board between the handles of two wooden spoons, and carefully slice at just under ½cm intervals all the way along (the spoons will stop you going all the way through).
Repeat with the rest of the potatoes.
Stir the stew, season to perfection, then push in the potatoes, cut side up.
Cook in the oven for 1 hour 30 minutes, or until the potatoes are golden and have sucked up loads of that lovely flavour.