Set oven at 400ºF. In a pan toss together olive oil, grapes and sliced leeks until well coated with oil, then season to taste with salt and pepper. Roast in the oven for 20 minutes, or until the grapes have begun to burst and are soft. Remove from oven and let cool.

Roll out puff pastry onto a lined baking sheet. Break up the goat cheese and dot all over the pastry. Using a slotted spoon place roasted grapes and leeks on top of goat cheese trying to drain out some of the liquid released by the grapes. Fold edges of pastry oven the filling and pinch the corners to seal.

Bake for 15 minutes, or until pastry is golden, then remove from oven and let sit for 5 minutes before slicing and serving – drizzle with remaining liquid from the pan the grapes were roasted in and top with sliced green onions to garnish.