Preheat the oven to 350 degrees F. Line a 9x13 pan with parchment paper and spray with nonstick spray.

Mix together the crushed graham crackers, butter and sugar until thoroughly covered in butter. Spread the crumbs into the base of the pan. Use the base of a cup or measuring cup to press the cracker mixture firmly into an even layer. Packing it down well makes sure the bars don’t crumble.

Bake for 7 minutes, and then remove from the oven to cool a bit.

In a large bowl, cream together the butter and sugars. Then, add in the eggs and vanilla and mix well. Add the flour in two additions, making sure to stir the mixture in between each addition. Sprinkle the salt and baking soda on top of the first addition of flour so that it can get mixed in. Combine the mixture until the flour is just incorporated.

Add ¾ of the marshmallows and 3/4 of the chocolate chips to the cookie dough mixture and mix until well disbursed

Carefully spread the cookie dough on top of the crust and bake for 18 minutes.

After removing the bars from the oven, scatter remaining marshmallows, chocolate chips, and place the chocolate squares on top of the bars and bake for an additional 9-11 minutes, or until it is golden brown on top. You want soft and gooey bars so be sure not to over bake them!