Gather all ingredients.

Place butter in a 2 ½ quart glass or metal bowl. Place the bowl over a 3-quart saucepan of gently boiling water. Cook over the simmering water until butter is melted.

Add chocolate chips; stir until melted, then remove from heat. Let cool 10 minutes at room temperature, stirring occasionally.

Add marshmallows to melted chocolate; gently stir to coat.

Place two 15x18-inch pieces of parchment paper on work surface. Place half of the chocolate-marshmallow mixture onto the middle of each piece of parchment and shape into a 12-inch long log using a rubber spatula.

Wrap logs tightly in the parchment and transfer to refrigerator; chill logs for 30 minutes.

Place two new 15x18-inch pieces of parchment paper on work surface and sprinkle each with 1 cup flaked coconut. Carefully transfer chilled logs to the new pieces of parchment with coconut.

Roll logs in coconut and gently press to fully cover outside and sides.

Wrap coated logs tightly in the new parchment paper and chill until firm, at least 4 hours up to overnight.