Combine chocolate and butter in top of a double boiler. (I use a smaller saucepan sitting just inside a larger one with just enough water on the bottom of the larger pan so that it doesn't quite touch the top one); bring water to a boil.
Reduce heat to low; cook and stir until chocolate melts.
Cool to lukewarm.
Put marshmallows and nuts in large bowl (use glass if possible, easier to clean up).
Add melted chocolate to marshmallows and nuts and mix.
Using waxed paper, shape into 2 rolls 2" in diameter, twisting the ends to seal.