1For the Pastry:
In bowl of food processor fitted with metal blade, pulse flour, salt and sugar to combine. Add butter and pulse until flour resembles coarse, uneven cornmeal, about 10 one-second pulses. Drizzle 5 tablespoons ice water over mixture. Pulse several times to work water into flour. Add remaining water, 1 tablespoon at a time, and continue pulsing until mixture develops small curds. Turn dough out onto work surface, shape into a disc and cover in plastic wrap. Refrigerate at least 1 hour.
2On lightly floured surface, roll half the dough to 1/16-inch thickness. Cut out 6 (4 1/2-inch) circles. Ease dough circles into a 12-cup (4-ounce capacity) nonstick muffin pan, pressing out any overlap. Repeat with remaining dough. Place in freezer 5 minutes. Trim overhang with knife. Line dough cups with cupcake papers and fill with dried beans or pastry weights. Bake at 350 degrees 10 minutes to set.
3For the Custard:
Dissolve cornstarch in 1/4 cup cream in medium bowl. Add remaining cream and sugar and stir until mixture is smooth and sugar dissolves. Check for sugar granules with a spoon; none should remain. In small bowl, blend yolks with fork until smooth. Add to cream mixture, stirring gently to combine.
4Ladle egg mixture into partially baked pastry cups, filling to 2/3 capacity. Bake at 350 degrees until edges of custard are puffed and middle is still jiggly, 20 to 25 minutes. (Custard will continue to cook after removing from oven.) Cool completely in pan. Best when eaten the same day.