Heat oven to 350°F. In medium bowl, break up cookie dough. Knead in chocolate until well blended. Shape rounded tablespoonfuls of dough into balls. On ungreased cookie sheet, place balls 2 inches apart. With bottom of glass, flatten slightly.
Bake 10 to 12 minutes or until set. Cool 2 minutes on cookie sheet. Remove from cookie sheet to cooling rack. Cool completely, about 30 minutes.
For each sandwich cookie, spread 1 tablespoon frosting on bottom of 1 cookie. Top with second cookie, bottom sides together; press together gently.