In a food processor, combine the flour, sugar and salt. Add the butter and pulse until the mixture resembles coarse sand. Add the egg, water and vanilla. Pulse until the dough just begins to hold together. Remove the dough from the food processor and shape into a log. Cut into 8 pieces and shape by hand into 8 discs. If the dough is too soft to work, place the discs on a plate, cover and refrigerate for about 30 minutes.
