Place chocolate chips in a microwave-safe bowl and heat it for 30 seconds in the microwave. Stir the chips, then heat them for additional 30 seconds. Stir the chips again until smooth. Heat further for 15-second intervals and stir as needed until all the chocolate is smooth. Be careful not to overheat the chocolate, or it will burn. Place melted chocolate in a Ziploc bag and snip the corner off. Drizzle the melted chocolate over the cookies for a garnish.