ADD heavy whipping cream to a saucepan and heat over medium heat, stirring occasionally until heated through but not boiling. Remove pan from heat.
STIR in chocolate bars, kosher salt, butter and vanilla. Continue stirring until chocolate has
melted and mixture is smooth and creamy. Pour into a shallow bowl for dipping.
TO assemble, place 1 to 2 mini marshmallows on a toothpick. Dip into chocolate fondue, then place on a mini graham cracker (pressing firmly will poke the toothpick through the graham cracker, so it becomes a one bite treat.)