How to Make It
In a spice mill, grind 1/4 cup of the sesame seeds to a fine powder. In a food processor, pulse the ground sesame seeds with the flour, cornmeal and salt. Add the oil and process until the mixture resembles moist sand. Add the water all at once and pulse just until incorporated. Turn the dough out onto an unfloured work surface and knead just until smooth. Wrap the dough in plastic and let rest for 15 minutes.
Preheat the oven to 375°. Divide the dough into 4 pieces. On a lightly floured surface, roll out 1 piece of dough 1/8-inch thick; keep the rest wrapped. Sprinkle 1 tablespoon of the sesame seeds over the dough and press them into the pastry with a rolling pin. Cut the pastry into 1-inch squares and transfer to ungreased baking sheets. Repeat with the remaining dough and sesame seeds.
Bake the crackers in the upper and lower thirds of the oven for 20 minutes, or until golden and crisp, shifting the pans from top to bottom and front to back halfway through. Let the crackers cool completely on the baking sheets.