Preheat your oven:
Set oven to 350°F (175°C). Line an 8×8-inch baking dish with parchment paper or lightly grease it with nonstick spray.

Make the cookie dough:
In a mixing bowl, cream together the softened butter and brown sugar for about 2 minutes until light and fluffy. Add the egg and vanilla, mixing just until combined.

Add dry ingredients:
In a separate bowl, whisk together gluten free flour, graham cracker crumbs, baking powder, and salt. Add to the wet ingredients and mix until combined. Let the dough rest for 5 minutes to hydrate.

Assemble the layers:

• Press a little more than half the dough evenly into the bottom of the pan.

• Gently spread the marshmallow fluff over the top. (Tip: dip the spoon in water to prevent sticking!)

• Sprinkle chocolate chips evenly over the fluff.

• Drop the remaining dough by spoonfuls over the top — no need to cover it completely.

Bake:
Bake for 30–35 minutes, or until the top is golden brown and the edges are set. The center may still look a little soft — that’s the gooey marshmallow layer.

Cool and rest:
Allow bars to cool completely, then rest for at least 12 hours before slicing for best texture. Chill for an hour if you want clean, bakery-style cuts.

Serve and store:
Cut into small squares and enjoy! Store leftovers covered at room temperature for up to 3 days, or refrigerate for up to 5 days.