Preheat oven to 350 degrees F (175 degrees C). Melt 1/2 cup chocolate chips in microwave or double-boiler, stirring occasionally until smooth. Cool to room temperature. In a small bowl, dissolve instant coffee in boiling water; set aside.
In a large bowl, cream together the butter, white sugar, and brown sugar until smooth. Beat in egg, coffee, and melted chocolate. Combine flour, baking soda, and salt; mix into batter. Stir in the remaining chocolate chips and walnuts. Drop dough by heaping teaspoons onto ungreased cookie sheets.
Bake for 10 to 12 minutes in preheated oven. Allow to stand 2 to 3 minutes on the cookie sheets before transferring to wire racks to cool completely.
