Step 1: Prepare the Baking Pan and Preheat the Oven
To begin, line an 8-inch or 9-inch square baking pan with parchment paper. Leave an overhang of parchment on the sides to make it easier to lift the bars out of the pan once they’ve cooled. This step is important as it prevents the bars from sticking to the pan. After prepping the pan, preheat your oven to 350°F (177°C).

Step 2: Make the Graham Cracker Cookie Dough
In a large mixing bowl, use a handheld or stand mixer with a paddle attachment to cream together the softened butter and brown sugar. Beat on medium-high speed for about 2 minutes until the mixture becomes light and fluffy. Then, add the egg and vanilla extract, mixing until everything is well combined. Don’t worry if the mixture looks slightly curdled at this point; that’s perfectly fine.

In a separate bowl, whisk together the all-purpose flour, graham cracker crumbs, baking powder, and salt. Once the dry ingredients are well combined, gradually add them to the wet ingredients. Continue mixing on medium speed until a thick dough forms.

Step 3: Assemble the Layers
Now it’s time to layer the ingredients into your prepared pan. Start by dividing the graham cracker dough into two portions—one slightly larger than the other. Press the larger portion of dough into the prepared pan, spreading it out evenly to form the base layer. This dough will be sticky, so feel free to use your hands to press it into place.

Next, spread the marshmallow creme evenly over the cookie dough base. This step may be a little tricky since marshmallow creme can be sticky, but use a spatula or spoon to spread it out as evenly as possible. Once the marshmallow layer is in place, sprinkle the chocolate chips evenly over the top.

Finally, take the remaining cookie dough and flatten it into pieces. Layer this over the chocolate chips. Don’t worry if it’s not a perfect covering—some chocolate chips and marshmallow creme may be exposed. That’s part of the charm!

Step 4: Bake the Bars
Place the pan in the preheated oven and bake the bars for 25-30 minutes. You’ll know they’re done when the top is golden brown and slightly firm to the touch. If you want a firmer texture, you can bake them a little longer, but be sure to watch them closely to prevent overbaking.

Once baked, remove the pan from the oven and place it on a wire rack to cool completely. Allow the bars to cool in the pan for at least an hour before attempting to cut them. This ensures they set properly and hold their shape.

Step 5: Cool, Cut, and Serve
Once the bars have cooled completely, use the parchment paper overhang to lift them out of the pan. Place them on a cutting board and slice them into 16 even squares. These bars are the perfect treat to enjoy with a cold glass of milk or a cup of hot cocoa.

Store any leftover bars in an airtight container at room temperature for up to a week. You can also freeze them for later enjoyment.