1 cup firmly packed light brown sugar
1/2 cup butter or margarine, softened
1 egg
1 teaspoon vanilla
2 cups all-purpose flour
2 teaspoons baking powder
1/4 teaspoon salt
2 tablespoons unsweetened cocoa powder
Beat brown sugar and butter in large mixing bowl until light and fluffy. Add egg and vanilla; beat until creamy. Stir together flour, baking powder, and salt; gradually add to sugar mixture. Divide dough in half. Add cocoa to one-half dough. Roll dough separately on floured waxed paper into 2 rectangles about 1/4-inch thickness. Top one with the other and press together with a rolling pin. Roll up lengthwise, jelly roll fashion. Trim edges; wrap and chill until firm. Once roll is chilled, remove from refrigerator. Preheat oven to 350. Cut roll into 1/4 inch slices and bake on well greased cookie sheets 12 to 15 minutes.
