Preheat your oven to 350°F (175°C) and prepare your baking pan by lining it with parchment paper.

Combine crushed graham crackers with melted unsalted butter, then press the mixture into the bottom of the baking pan. Bake for 10 minutes.

In a bowl, blend together the brown sugar, granulated sugar, and melted butter until smooth and creamy.

Add in the eggs and vanilla extract, whisk until fully combined and smooth.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add this to the wet mixture, stirring gently.

Fold in the chocolate chips, then pour the batter over the prepared graham cracker crust, smoothing it out.

Sprinkle mini marshmallows and more chocolate chips on top of the batter.

Bake for 30 minutes until the edges are golden brown and the center is set but soft.

Allow to cool in the pan for at least 15 minutes before lifting out and slicing into squares.