Pre heat the oven to 230°C, Gas 8.
Heat a large frying pan.
Season the racks of lamb all over with salt and pepper really well.
Add 2 tbsp veg oil to the hot pan and then add 2 of the racks of lamb and seal well all over.
Place in a baking tray, skin side down and cook for 12-15 minutes.
Remove from the oven, turn over and cook for a further 8-10 minutes, then remove from the oven and cover with foil and keep warm. Rest for 20 minutes in a warm place.
To make the hollandaise place the vinegar, wine, peppercorns and mint stalks into a pan and bring to the boil.
Boil rapidly until the liquid has reduced by half to ¾’s then strain out the peppercorns and stalks.
Add the reduced liquid back to the pan and add the butter and again bring to a rolling boil.
Place the egg yolks in a liquidiser and blitz for 10 seconds to break up.
Gradually and carefully add half the boiling vinegar and butter mixture into the liquidiser in a thin stream, through the lid.
Re boil the pan and pour the rest onto the eggs.
Pour sauce back into the pan and stir well, and taste the sauce and adjust the seasoning adding a squeeze of lemon juice and fresh mint, cover and keep warm, it will thicken slightly.
Serve the warm sliced lamb, the warm hollandaise spooned over.