COMBINE butter, condensed milk, cocoa powder, and salt in a saucepan. Boil mixture over medium heat, stirring constantly, for about 5 minutes.
ADD chocolate and marshmallows. Mix well until marshmallows are melted. Add chopped M.Y. San Grahams Chocolate. Cool.
SCOOP 1 tablespoon of the mixture and drop onto a wax paper. Repeat the procedure for the rest of the mixture.
CHILL and SERVE