Melt together the butter and chocolate chips in the top of a double boiler or in the microwave. Stir to blend, then stir in the eggs, colored marshmallows and pecans.
Pour the mixture into a 9x5 inch loaf pan, lined with wax paper or cling wrap. Dust with powdered sugar (optional, I skipped it) and refrigerate until firm, at least 12 or even 24 hours is best.
Remove chilled dough from loaf pan, remove the wax paper or cling wrap. If desired, roll in shredded coconut. Slice into 1/4 inch slices.
Notes
This recipe needs to be stored in the refrigerator and can be made a day ahead.