Peel the potatoes and cover with water. Add the mint, half the butter and salt and pepper. Cook until al dente and leave to cool in the water. Drain when cool, cut in half lengthways and set aside.Peel the shallot and slice finely into ring. Cover with white wine vinegar. Set aside for a minimum of 1 hour before draining the vinegar.Warm the pre-cooked tentacles through in their packaging for 1 hour in simmering water, then refresh the pack in ice-cold water. Once cold, remove from the packaging and slice on an angle into 1 inch pieces.Heat a chargrill pan. Add a little olive oil, then the octopus. Season and cook for around 2 min on each side. Add the new potatoes to the hot pan and cook until caramelised.Arrange the potatoes and octopus on a serving dish. Scatter the shallot rings and caper berries. Finish with dots of aioli and dust with paprika. Serve with wedges of lemon on the side.