Preheat the oven to 350 degrees F. Line a 9x13-inch pan with foil, leaving a 2-inch overhang on the 2 short sides. Grease the foil with cooking spray and set aside.

In a large bowl or the bowl of a stand mixer, beat the butter and sugar together until light and fluffy, about 2 minutes.

Beat in the eggs and vanilla until well combined.

Add the flour, graham cracker crumbs, baking powder, and salt to the bowl, and stir well to combine. Stir until it forms a thick dough and everything is well incorporated.

Divide the dough in half, and press half into the bottom of the prepared pan until the dough is evenly flattened.

Dollop the marshmallow topping on top of the cookie base and gently spread into an even layer. (“Spread” in theory… it’s a stick mess, so just blop it on there as best as you can. It’ll taste good even if it’s not terribly even.)

Sprinkle the chocolate chips on top of the marshmallow cream.

Scatter the remaining dough over the top in clumps. Don’t worry about completely covering the top; the marshmallow and chocolate chips should peek through. Sometimes I take little pieces of the dough in my hand and flatten them a bit before putting it on top of the chocolate chips -- whatever works for you. And if you can stand it, this is a great step to let kids help with. It’s kind of fun!

Bake the bars until golden brown, about 30 to 35 minutes. Cool completely. Remove the bars from the pan using the foil overhangs.

Cut into bars and serve.

This is a great recipe to make ahead of time (up to a day ahead) and take to a party, picnic, party, or dinner with friends.