Preheat the oven to 170°C and line a baking pan (22.8x22.8cm) with parchment paper.

Place graham crackers evenly on the bottom of the pan.

Melt butter and mix with sugar in a bowl until well combined.

Add salt and cocoa powder to the butter mixture and stir well.

Add eggs and vanilla extract, breaking the yolks first, and mix thoroughly for about 2 minutes.

Fold in the flour gently using a spatula, lifting and cutting through the batter.

Add chocolate chips and mix lightly.

Pour the batter over the graham crackers in the pan and spread evenly.

Bake in the preheated oven for 23-25 minutes. Check doneness with a toothpick; it should come out with a few crumbs.

Cool the brownies in the pan for 20 minutes, then transfer to a wire rack to cool completely.

Microwave marshmallows for about 20 seconds until puffed.

Stretch the melted marshmallows and drape them over the brownies to create a spiderweb effect.

Press the marshmallow decoration lightly onto the brownies and let it set completely.