In a large saucepan, melt the butter and semisweet chocolate chips over low heat. Remove the saucepan from the heat and add the vanilla, salt, and walnuts. Cool for 15 minutes.
Add the marshmallows and stir until combined.
Spoon half the mixture lengthwise down the center of a piece of waxed paper and roll it into a log. Sprinkle the coconut on and roll the log, evenly coating the outside. Wrap the log in waxed paper. Repeat with the remaining dough.
