In a large heavy bottom pot, heat 2 - 3 tbsp of olive oil.
Place lamb racks in fat down and leave for 4 - 5 minutes or until golden brow & caramelised.
Turn and seal all sides of the rack.
Throw in garlic cloves whole and bay leaves then add about 1 cup of the red wine vinegar and the balsamic vinegar and the red wine, keep over high heat. Use some aluminium foil and place inside the pot covering the roast but allowing some steam to escape around edges. Be careful, the fumes from the vinegar can really take your breath away!
Cook over high heat for about 45 minutes but keep a close eye on it, do not allow to boil dry, use the remainder of the bottle of red wine vinegar to ensure it does not boil dry. The vinegar and fat from the lamb will emulsify and create a lovely rich thick sauce.
Boil potatoes skin on until cooked, drain and add about 1 tbsp butter and 1/2 cup milk and the spinach, using something solid like end of rolling pin crush the potatoes. Don't use a masher as you don't want to mash them too much. After crushing just stir to make sure spinach and butter is stirred though, season with P&S to taste.
Also great served with broccolini on side.
When you cut the rack it should still be a little rare drizzle a little of the sauce on the cutlets before serving and a garlic clove or 2 and a bay leaf on each looks great too.