In a medium bowl, stir together the flour, salt, white pepper and mustard. Cut in butter with a fork until the mixture resembles coarse crumbs. Stir in Cheddar cheese. Stir in water one tablespoon at a time, until the dough is able to hold together. Press the mixture into a ball, wrap and refrigerate for at least 30 minutes.
Preheat the oven to 350 degrees F (175 degrees C). Line baking sheets with parchment paper.
On a lightly floured surface, roll the dough out to a rectangle that is 16x12 inches. The dough should be about 1/8 inch thick. Cut into 1x3 inch strips. Place the strips onto the prepared baking sheets spaced about 1 inch apart.
Bake for 10 to 12 minutes in the preheated oven, or until golden and crispy. Cool completely before storing.