Line 8” x 8” pan with wax paper, letting the ends hang over the edges. You will use these as handles later.
In a saucepan over medium heat, combine the chocolate chips, Nutella and butter. Heat, stirring constantly, until melted and smooth. Remove from heat and add vanilla. Let cool until pan is safely touchable on the bottom but still smooth to stir.
Stir in coconut to combine well. Stir in marshmallows to cover.
Spread mixture evenly in prepared pan. Place a sheet of clear wrap over the top and press mixture firmly and evenly down into pan to make an even top.
Chill in refrigerator, covered with the plastic wrap, for at least 3 hours before cutting into squares. Remove from refrigerator just before serving.
Notes
Wrap well and keep in an air-tight container in the fridge for up to for 10 days.