Roll out the puff pastry to 3-4mm thickness on a floured surface and prick with a fork.
Cut out four 23cm discs and rest them in the fridge.
Preheat the oven to 200°C.
Thinly slice the peeled and cored apples.
Place pastry discs on a buttered tray and brush edges with melted butter.
Spread membrillo in the center of each disc and layer the apple slices on top.
Drizzle with honey, sprinkle with sugar, and bake for 5-6 minutes until brown.
Whip the double cream until thick and fold in walnuts and honey.
Glaze the warm tarts with remaining butter and serve with the walnut cream and mint.