Line a buttered 8x8 pan with parchment paper.
Place nuts,heath bits, chocolate, butter and vanilla in a bowl.
In a heavy saucepan, cook sugar, milk and marshmallows over low heat until it comes to a boil. cook 6 minutes, stirring constantly. Whisk in espresso powder. Pour into bowl with chocolate and mix. spread into pan and sprinkle the top with some heath bits. Cover and chill in the refrigerator.
Bring to room temperature to cut into small squares. Enjoy!