or margarine, softened
Preheat the oven to 350℉ (180℃).
In a large bowl or in the food processor, cut the butter into the flour until the mixture resembles coarse meal.
Add the cheese and egg yolk and mix well.
Add enough of the water to form a dough that will hold together in a cohesive ball.
The texture will be somewhat crumbly, but the dough will hold together when pressed.
Divide the dough into 2 equal portions for rolling.
On a floured surface or pastry cloth, roll each into a rectangle about ¼ inch thick.
Cut out individual crackers about 2 inches across with a cookie cutter or sharp knife and arrange them on an ungreased baking sheet.
Prick each cracker 2 or 3 times with the tines of a fork.
Bake for 10 minutes.
Turn the crackers over and bake another 5 to 10 minutes, or until medium brown.
Cool the crackers on a rack.