In a small bowl, microwave two-thirds of the chocolate at medium (50%) power for 2 minutes. Stir, then heat at 1-minute intervals, stirring after each, until the chocolate is melted and warm to the touch. Stir in the remaining chocolate and let stand for 5 minutes; stir until smooth.
Place a sheet of parchment on a work surface. Dip the rounded end of a cookie into the chocolate to coat. Remove any excess chocolate by scraping the cookie on the edge of the bowl; transfer to the parchment. Repeat with a few more cookies; sprinkle with nuts before the chocolate sets. Repeat with the remaining cookies, chocolate and nuts. Let stand until the chocolate sets, about 30 minutes.