Line a 9x9 inch pan with foil and then grease lighly with butter.

Place chocolate chips and sweetened condensed milk in a bowl and microwave for 1 minutes.

Stir and then microwave in 15 second increments until chocolate is melted and smooth.

Mix in the marshmallows and nuts and pour into pan.

Place in fridge for 2+ hours until set and then cut into squares.

Store in an air tight container in the fridge.