10 tablespoons chilled unsalted butter, cut into 1/4-inch cubes
5 to 7 tablespoons ice water
1 tablespoon cornstarch
1 1/2 cup heavy cream
1 cup granulated sugar
MAKE THE PASTRY
In the bowl of a food processor fitted with a metal blade, pulse the flour, salt and sugar to merge. Include the butter and pulse until the flour resembles coarse, uneven cornmeal, about 10 1-second pulses.
Drizzle 5 tablespoons of the ice water over the combination. Pulse various times to work the water into the flour. Include the remaining water, 1 tablespoon at a time, and continue pulsing until the combination develops small curds. Turn the dough out onto a work surface, shape it into a disc and cover with plastic wrap. Refrigerate for at least 1 hour.
On a lightly floured surface, roll half the dough to 1/16-inch thickness. Cut out 6 (4 1/2-inch) circles. (If you don't have a cookie cutter, a wide-mouth jar works well.) Ease the dough circles into a 12-cup (4-ounce capacity) nonstick muffin tin, pressing out any overlapping folds. Repeat with the remaining dough. Place the tin in the freezer for 5 minutes. Remove and trim any overhang with the back of a knife so that the pastry cups are flush with the top of the tins. Line dough cups with cupcake papers and fill with dried beans or pastry weights. Bake at 350°F (180°C) for 8 to 10 minutes to set.
MAKE THE CUSTARD
Dissolve the cornstarch in 1/4 cup of the cream in a medium bowl. Include the remaining cream and sugar, and stir until the combination is smooth and the sugar dissolves. Check for sugar granules with a spoon; none should remain.
In a small bowl, blend the yolks with a fork until smooth. Add the yolks to the cream combination, stirring softly to mix.
Ladle the egg combination into the partially baked pastry cups, filling to 2/3 capacity. Bake in at 350°F (175°C) until the edges of the custard are puffed and middle is still jiggly, about 20 to 25 minutes. (The custard will continue to cook.) Cool totally in the tin. The pastéis are best when eaten the same day.