Combine the butter and chocolate chips in a large saucepan over medium-low heat. Cook, stirring frequently, until the chocolate and butter are both melted and the mixture is smooth.

Turn off the heat and then very slowly, whisking continuously, pour in the eggs. Continue to whisk until smooth. Add in the powdered sugar, 1/4 cup at a time, until completely incorporated until smooth.  Stir in the marshmallows. Refrigerate the mixture until it starts to set up.

Lay down a piece of parchment paper or wax paper. Sprinkle 1/3 of the coconut over the top. Divide the chocolate/marshmallow mixture into 3 equal portion. Place one portion of the mixture on the coconut and form it into a log, about 1 1/2” thick and 8 inches long. (I found that it is easiest to do with greased hands.)  Roll the log over the coconut, pressing the coconut into the sides to adhere. Transfer the coconut covered log to a piece of plastic wrap and wrap tightly. Repeat with the remaining 2 portions.

Refrigerate the candy until set up, at least a couple hours, up to 3 weeks. When ready to serve, unwrap the log and cut it into 1/2-inch slices.