Place sesame seeds in a heavy-bottomed skillet over medium-high heat. Toast, stirring constantly, 5 to 8 minutes, until the seeds are brown. Transfer to a plate or small bowl to cool completely (20 minutes).

Preheat oven to 325°F. Line baking sheets with parchment.

In the bowl of a food processor, combine flour, 2 tsp toasted sesame seeds, salt, and red pepper. Run processor for 20 to 30 seconds, or until seeds are ground.

Place butter on top, and pulse 5 to 6 times to cut in. The resulting mixture will look like coarse corn meal.

Add 2 tablespoons ice water and pulse several times to combine.

Add 1 tablespoons toasted sesame seeds, pulse to combine.

Add remaining 2 tablespoons ice water and run processor until a dough forms and rides on the blade.

Place dough on a lightly-floured surface and shape into a disk 4 inches in diameter. Divide into 4 pieces. Roll each piece of dough to a thickness of 1/16-inch. Sprinkle with 2 teaspoons of toasted sesame seeds, and lightly roll in. Cut into 1-inch squares and place on parchment-lined baking sheet. Repeat with remaining dough.

Bake 23 to 25 minutes or light golden brown. Let cool completely on the baking sheets before packing into airtight tins.