Leave butter on the counter to soften.
Add graham crackers to the food processor. Grind completely (skip if using graham cracker crumbs).
Preheat oven to 350°F.
Line baking tray (9” x 13”) with parchment paper.
To the cake mixer, add softened butter and brown sugar.
Combine until light and fluffy (approx. 2 minutes).
Add eggs and vanilla. Combine fully (another 1-2 minutes).
In a separate bowl, add the ground graham cracker crumbs, flour, baking powder and salt.
Mix thoroughly.
Add the dry ingredients to the stand mixer, a little at a time until fully combined.
Divide the thick cookie dough batter into 2.
Press one half of the batter onto the base of the baking tray.
Spread the marshmallow fluff on top. Be gentle.
Sprinkle chocolate chips on top of the fluff.
Add chunks of the remaining cookie dough batter on top.
Bake for 30 to 32 minutes.
Remove from the oven.
Add additional toppings [optional].
Set aside to cool.
Lift the parchment paper out of the baking tray.
Cut the baked dessert into 24 smores cookie bars.
Serve warm or cold. Store in fridge for 2-3 days or freezer for months.