In large microwaveable bowl, combine chocolate, milk, butter, and salt. Place bowl in microwave and heat on high for 3 minutes, stirring every 30 seconds. Remove and whisk until combined and smooth. (If chocolate is not completely melted after whisking, return to microwave for 1 minute and repeat step.) Stir in pistachios and cherries. Line the bottom and sides of a 9 x 9-inch pan with plastic wrap. Pour chocolate mixture into pan, scraping bowl, and smooth out evenly. Refrigerate until firm, about 1 hour. Remove pan from refrigerator and invert chocolate mixture onto a cutting board. Remove plastic and cut chocolate with a knife into desired shape and size. Serve at room temperature.