Heat oven to 450 degrees.
Remove puff pastry from refrigerator. Working quickly, arrange the mango slices in overlapping circular patterns on pastry rounds, leaving a 1/4-inch border. Be sure to tuck a small piece of mango into the center of each tart. Brush mango slices with melted butter, and sprinkle each tart evenly with about 1 teaspoon sugar.
Makes 8 tarts.