In a medium bowl, cream the butter and sugar together until light and fluffy. Beat in the egg and vanilla. Combine the flour, baking soda and salt and sift into the butter mixture. Blend thoroughly. Stir in the pecans. Shape the dough into a roll 2 inches in diameter. Wrap tightly in plastic wrap and refrigerate overnight or for up to 1 week. Preheat the oven to 350 degrees F. Using a sharp thin knife, cut the dough into 1/4-inch slices and place on ungreased cookie sheets. Bake in the center of the oven for about 15 minutes, or until lightly browned and set. Transfer to wire racks to cool. Makes 48 cookies * Recipe by Joanna Pruess * Great Desserts, compiled and edited by Mardee Haidin Regan * Typed for you by Karen Mintzias