Make the tart shells first. Brush 6 tart molds with removable bottoms with the melted butter. In a food processor, combine the flour, butter and sugar. Pulse for a few seconds until crumbly. Add the egg and pulse till dough turns a ball. Wrap the dough in plastic wrap and let rest at room temperature for half an hour.
Divide the dough in six portions and on a floured surface, roll each portion into a large circle that will fit the tart mold. Leave ¼ inch overhang. As the recipe suggests, the dough will shrink. Press the dough along the sides of the pan and prick the bottom with a fork. Refrigerate for 30 minutes or more. Preheat the oven to 375 F degrees. Bake the shells for 15 minutes till brown. Let cool on racks before removing the shells from the molds.