MELT chocolate over boiling water or in microwave. Set aside until ready to use.
SPOON flour, baking powder & salt in small bowl.
CREAM sugar, butter, shortening, egg & vanilla thoroughly.
ADD dry ingredients to creamed mixture. Mix well.
SPRINKLE water over combined ingredients. Stir to blend.
DIVIDE dough in half. Add melted chocolate to one portion of dough, mixing well.
ROLL OUT each portion of dough between wax paper to a 6x4 inch rectangle.
REMOVE top sheet of wax paper. Place chocolate dough over vanilla dough. Cover with wax paper and roll combined doughs to rectangle 1/4 inch thick.
ROLL UP lengthwise, jelly-roll fashion, guiding roll with wax paper.
CHILL 1 1/2 to 2 hours until firm.
SLICE with sharp knife to 1/8 inch thickness.
PLACE on ungreased baking sheet.
BAKE at 400º for 8-10 minutes.