between the palms of your hands to for 1-inch balls. If you are using the optional nut coating, roll each ball in the reserved egg whites. Lightly flour your hands, if necessary, to prevent sticking. Roll each ball in the chopped nuts. Place the balls 1 1/2 inches apart on the cookie sheets. Use your floured index finger to create depressions in the center of each ball. Fill each depression with 1/4 teaspoon of the remaining jam. Bake for 20 minutes or until the cookies begin to brown lightly. Store in airtight containers at room temperature or in the refrigerator. Keeps 1 week at room temperature, 2 weeks refrigerated. The squares will keep for several weeks refrigerated. The thumbprints become dry. Makes 16 squares and 3 dozen cookies. Original from Rose's Christmas Cookies by Rose Levy Berenbaum This recipe makes both Linzer Squares and Thumbprints, although you need a pastry bag to pipe the dough to make the Linzer Squares. I used the whole recipe to make thumbprints. I made just the thumbprints, not the linzer squares. If you do this as well (it's EASIER), be sure to add the 3 tablespoons of egg white into the dough. The instructions to do this are in the section labeled "for the Squares" and you might miss it if you're not making the squares.