Place the vinegar, wine, pepper 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.
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 (this is really important, or the yolks will not thicken) into the liquidiser (not a food processor) in a thin stream on full speed, 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, salt and chopped mint leaves, cover and leave for 5 minutes.
After 5 minutes uncover stir well, you may need to add a little water if too thick.