Mix the fruit with the mint and lemon juice, cover and leave to infuse for approx. 1 hr.
Toast the hazelnuts in a frying pan over a medium heat until golden brown, transfer to a clean tea towel, rub off the skins. Bring the sugar and water to the boil in a wide pan without stirring. Reduce the heat and simmer, swirling the pan occasionally until a light brown caramel has formed. Add the cinnamon, oil and hazelnuts, mix, immediately spread onto a sheet of baking paper, leave to cool, coarsely chop.
Plate up the fruit salad, top with the nut brittle.