Preheat oven to 375°F (190°C). Grease and flour cookie sheet. Process flour, egg, and guar gum in food processor, then pulse butter 1 tbsp at a time, until dough is like a coarse meal. Gradually add just enough water so that mixture sticks together when pressed with hand. Roll out with flour between two sheets of parchment paper. Peel off the top, place it back on and peel off the other side. Slice into shapes and place on sheet. Bake 10-15 min.