Roll out pastry to 0.2cm thick and cut out 6*12cm circles. Prick all over with fork and place on baking sheet lined with baking parchment. Chill for 1hr.
Preheat oven to 200C. Peel, core and quarter apples, then slice as thinly as poss. Lay in circular pattern around pastry discs, overlapping and tucking last slice under first to form even pattern.
Brush apples with half melted butter and scatter generously with caster sugar. Bake for about 30mins until apples begin to caramelise.
mins before tarts are ready, lightly whip double cream with sugar and vanilla. Brush hot tarts with remaining melted butter and serve with Chantilly cream.