01 -
Preheat oven to 177°C. Line an 8-inch or 9-inch square baking pan with parchment paper, leaving enough overhang to easily remove the bars. Set aside.
02 -
In a large bowl, use a handheld or stand mixer fitted with a paddle attachment to cream the butter and brown sugar together on medium-high speed for about 2 minutes. Add the egg and vanilla extract and beat until combined. Scrape down the sides and bottom of the bowl as needed.
03 -
Whisk together the flour, graham cracker crumbs, baking powder, and salt in a medium bowl. Pour the dry mixture into the wet ingredients and beat on medium speed until combined.
04 -
Press or spread two-thirds of the graham cookie dough into the prepared pan. The dough will be sticky, so use your hands if needed. It will form a thin layer.
05 -
Spread the marshmallow creme evenly on top. Layer the chocolate chips over the marshmallow creme.
06 -
Mold the remaining cookie dough into flat pieces and layer on top of the chocolate chips. Some chocolate chips and marshmallow will remain exposed.
07 -
Bake the bars for 25-30 minutes or until the top is lightly golden brown. Remove from the oven and place the pan on a wire rack to cool completely.
08 -
Lift the bars out using the parchment paper overhang. Cut into squares. Cover and store leftover bars at room temperature for up to 1 week.