Preheat the oven to 425 degrees and line a baking sheet with parchment paper.

Unroll the puff pastry dough and roll it out until it’s around 1/8th inch thick.

Cut the dough into 12 rectangles. Transfer the rectangles to the prepared baking sheet.

Break the chocolate bars into thirds and place one piece on top of each piece of dough. Bring the edges of the dough around the sides of the chocolate and pinch the ends together.

Brush the edges of each dough piece with egg.

Bake in the preheated oven for 10 to 12 minutes, until the pastry is golden brown.

Remove the pan from the oven. Lightly press two marshmallows into the top of the candy bar.

Return the pan to the oven and cook under the broiler for around 2 to 3 minutes, until the marshmallows are golden brown. Sprinkle the graham cracker crumbs over the top and serve immediately.