For the lamb: preheat the oven to 160C/140C fan/gas 3.
Melt the butter in a frying pan and add a dash of olive oil. Put the garlic and rosemary (or thyme) in the pan and fry for a few minutes on a low heat to flavour the oil and butter. Using a slotted spoon, remove the herbs and garlic and set aside.
Remove the cling film from the meat and season it with salt and pepper. Fry the lamb to brown it on both sides. Add the halves of garlic and allow them to colour slightly in the pan. Transfer everything to a roasting tin, along with the reserved herbs and sliced garlic.
Heat the wine in a small saucepan and then pour it over the lamb. Cover the tin with foil and place in the oven to cook for 45 minutes - 1 hour, or until the meat is meltingly tender.
Once cooked, remove the meat, cover and keep warm. Set the garlic halves aside too. If the liquid doesn’t look thick enough for a sauce, strain the wine and cooking juices into a saucepan, squeezing the juices from the rosemary and garlic skins.
Simmer the juices until thickened. To thicken the sauce even more, you can mix together equal quantities of flour and butter in a small bowl. Whisk this mixture into the sauce and cook until the taste of flour is removed. Add salt and pepper to taste. Keep the sauce warm.
For the mash: peel the potatoes and cut them into quarters. Put them in a steamer and add the thyme bundle. Steam the potatoes over a medium-high heat until they are easily pierced with a fork, about 20-30 minutes.
While the potatoes are cooking, purée the chives, parsley, olive oil and salt in a food processor to make a fairly smooth paste.
Put the milk, cream and butter together in a saucepan and warm, ensuring the butter has fully melted.
. When the potatoes are done, discard the thyme and press through a ricer into a large bowl (alternatively use a potato masher, but you will not get such a smooth finish). Pour in the hot cream butter mix and stir to combine.
. Just before serving, add enough of the herb mixture to colour the potatoes green and whisk until thoroughly incorporated, Add more salt or pepper as required.
. For the relish: blend all the ingredients in a food processor until finely chopped. Taste and add additional salt and/or sugar if needed.
. Serve the lamb steaks hot with the mash, relish, baked garlic and with the sauce poured over.