The flours are available at Whole Foods Markets. Makes about 60.
1 cup garbanzo bean flour
1 cup tapioca flour
1 tablespoon sugar
1 teaspoon coarse salt
1 teaspoon ground black pepper
6 tablespoons cold unsalted butter, cut into 12 pieces
6 tablespoons cold water
1 egg white mixed with 1 teaspoon of water
1. Set the oven at 400 degrees. Adjust a rack to the middle of the oven. Butter a 14-by-16-inch baking sheet.
2. In a food processor, combine the garbanzo bean flour, tapioca flour, sugar, salt, and pepper. Pulse for a few seconds just to mix the ingredients. Add the butter and pulse again until the mixture looks like coarse crumbs.
3. Add the water all at once while the machine is running. Stop when the dough turns into a ball. It will be soft but not sticky.
4. Place the dough directly onto the buttered sheet. Press it with your fingers or roll the dough into a rectangle about 12-by-14 inches, with a thickness of 1/8-inch. It is not necessary to use extra flour for this. Pierce the dough all over with a fork. With a knife or pastry wheel, cut the dough into crackers. The edges do not have to be even. Brush them with the egg white mixture.
5. Bake the crackers for 25 minutes, turning the sheet around after 10 minutes. Continue baking until the edges are brown. Remove any crackers at the edges that are browning too quickly. Transfer all the crackers to a wire rack to cool.
6. Store in an airtight container.