Honey Apple and Nectarine Tart with Whipped Mascarpone

Line 1 large baking sheet with parchment paper. Place the sheet of puff pastry on a floured surface and cut into 4 even squares. Separate the squares and leave some room between them on the baking sheet. Create a border around the inside of each square by scoring about 1/2-inch around the inside the square. Prick the dough inside the small square. Cover and refrigerate at least 30 minutes and up to 1 day. Position 1 rack in top third and 1 rack in bottom third of oven and preheat to 400 degrees F. On each pastry square, overlap slices of apple and nectarine , within the border. Brush fruit on each tart, with melted butter and sprinkle with 1 teaspoon sugar . Bake tarts until pastry is golden and apples are tender, about 20 minutes. Drizzle each tart with 1 teaspoon honey . Transfer tarts to racks; cool 5 minutes. Serve warm or at room temperature. While tarts are cooling, whisk mascarpone with orange liqueur. Top each cooled tart with a dollop of flavored mascarpone.