Mix thoroughly together: 1 cup soft butter, 1/2 cup sifted confectioners' sugar, 1 teaspoon vanilla. Sift together and stir in 2 1/2 cups sifted flour and 1/2 teaspoon salt. Mix in 3/4 cup finely chopped nuts; chill dough. Roll into 1" balls. Place on ungreased cookie sheet. Press thumb on top of each cookie, making a hole. Bake until set, but not brown in moderately hot, 400 degree oven, 10 to 12 minutes. Remove from oven and fill hole with jam or preserves. Cool if using icing.

EASY ICING: In small bowl stir 2 tablespoons melted butter, 1 tablespoon milk, 1 teaspoon vanilla and 1 cup confectioners' sugar until smooth. Frosts 4 dozen cookies.