Heat oven to 350 degrees F. Coat 13 x 9-inch baking pan with cooking spray.
Melt butter and chocolate in saucepan over medium heat. Remove from heat. Beat in sugar and dissolved coffee. Let stand 10 minutes, until just warm to the touch.
Beat in eggs until smooth. Stir in flour and 1 cup walnuts if using, just until combined. Scrape into prepared pan. Sprinkle with remaining walnuts.
Bake in 350 degree F oven for 30 minutes or until a wooden pick inserted in the center comes out clean. Cool completely in baking pan on wire rack. Cut into thirds lengthwise and tenths crosswise. Makes 30 brownies.