Prepare a baking sheet with parchment and set aside.

Add butter and salt to a deep skillet.

Let the butter melt and add the marshmallows.

Stir occasionally to help marshmallows melt. 

Once the marshmallows are almost melted turn the heat off and stir continuously to completely melt the last bits of marshmallow.

Put popcorn in a large mixing bowl, pour marshmallow mixture on top of the popcorn and mix until well incorporated.

Press popcorn onto the prepared baking sheet in order to create one layer.

Sprinkle Christmas sprinkles on top.

Sprinkle m&m’s on sprinkles.

Lightly press down so that sprinkles and m&m's stick to marshmallows.

Once cooled, break into pieces.