In a large pot, add the onion, bay leaf, carrots, parsnips and swede, brown with butter or oil for 10 minutes then remove from the pot
Stir in the lamb chunks and thyme and fry for 10 minutes until browned
Add the browned vegetables back into the pot
Pour over the lamb stock and bring everything to a gentle simmer
Skim any foam from the surface, then cook slowly for about 1½–2 hours until the lamb becomes tender and the broth develops deep flavour
Add the sliced leeks and potatoes and cook for another 10–15 minutes, letting them soften while still keeping their sweetness
Stir in the darker green leek tops right at the end
Taste and season generously with salt, pepper and lemon juice for brightness
Serve hot in deep bowls with plenty of bread for dipping and garnish with parsley and a wedge of cheese
