- With the rack in the middle position, preheat the oven to 200 °C (400 °F). Line a 43 x 30-cm (17 x 12-inch) baking sheet with parchment paper. Set aside.
- In a food processor, combine the flour and sugar. Add the butter and pulse until it is the size of peas. Add the buttermilk and pulse again until the dough begins to form.
- On a lightly floured surface (see note), knead the dough for about 1 minute or until smooth. Roll out the dough as thinly as possible until it is about the same size as the baking sheet. Place the dough on the baking sheet.
- In a small bowl, combine the egg and water with a whisk. Brush onto the dough. Sprinkle with salt and pepper. Bake for about 15 minutes or until the cracker is crisp and golden brown. Let cool on the baking sheet. Serving pieces in a serving dish or as is letting everyone break off chunks.
Because the dough is difficult to roll out, it is important not to over flour your work surface to allow the dough to slightly adhere to it. This will help you make it as thin as needed.