Place marshmallow cream and chocolate in a large bowl.
Bring sugar, milk, and butter to a boil in a large heavy saucepan, stirring constantly. Boil, stirring constantly, 8 minutes. Add to marshmallow cream mixture, stirring until chocolate melts. Stir in pecans. Drop by rounded teaspoonfuls onto wax paper-lined baking sheets; chill until firm. Store in refrigerator.