Preheat your oven to 375°F. Add the butter to a saucepan over medium heat. Melt the butter, then continue cooking and stirring until it becomes golden brown and develops a nutty aroma. Remove it from the heat.
Add the brown sugar and granulated sugar to a mixing bowl. While the browned butter is still very warm, pour it directly over the sugars. Whisk until smooth and glossy.
Let the mixture cool for 1-2 minutes so it isn't hot enough to cook the egg. Then add the egg and vanilla extract and whisk until fully combined.
Now add the flour, baking soda, and salt. Fold everything together just until combined. Fold the chocolate chips into the cookie dough.
Sprinkle the crushed graham crackers evenly across the bottom of a 9x9-inch baking dish.
Scoop the chocolate chip cookie dough directly over the crushed graham crackers. Gently press the dough into an even layer.
Arrange the large marshmallows over the top of the cookie dough to cover it entirely.
Place the dish in the oven and bake at 375°F for about 15 minutes, until the cookie is set around the edges and the marshmallows are puffed and golden brown. Do not broil.
Remove the s'mores pizookie from the oven and serve while it's still warm and the marshmallows are soft and gooey. Top with vanilla ice cream if desired and dig in!