Heat oven to 375 degrees. Place flour, sugar, and poppy seeds in food processor. Add butter; process until mixture resembles coarse meal, approximately 10 seconds.
With machine running, add ice water and egg yolks through the feed tube, and process until the dough holds together.
Turn dough out onto a piece of plastic wrap; press into a flat circle. Wrap in plastic, and chill for at least 1 hour.
Coat tartlet pans with cooking spray. On a lightly floured board, roll out dough to 1/8-inch thickness. Using a round 3 1/2-inch pastry cutter, cut out thirty-six circles. Press dough into molds, and place a second tartlet pan of the same size on top; press the two together lightly.
Bake 8 to 10 minutes; when the pastry begins to brown around the edges, remove the top pan, and continue baking until the pastry dries out and turns golden brown, 4 to 6 minutes. Transfer to a wire rack to cool completely. Store in an airtight container for up to 5 days.
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