The favorite combination of coffee and cocoa flavors these cookies, making a sophisticated treat for adults.
In a small bowl, stir together the flour, cocoa powder, coffee crystals, and salt. Set the mixture aside.
In a large mixing bowl, beat the butter with an electric mixer on medium to high speed for 30 seconds Add the 1/2 cup powdered sugar and vanilla; beat the mixture well.
Add flour mixture, beating on low to medium speed until combined. Stir in walnuts with a wooden spoon. Shape dough into 1-inch balls. Place balls about 1-1/2 inches apart on ungreased cookie sheets.
Bake in a 325 degree F oven for about 15 minutes or until the cookies are set. Cool on a cookie sheet for 1 minute. Transfer the cookies to wire racks.
While the cookies are still warm, roll in or sprinkle with some additional powdered sugar. Cool, then roll again in powdered sugar before serving. Store in a tightly covered container.