First things first, when it comes to cookies let your butter come to room temperature. I know it’s a pain and you kind of have to plan ahead, but it really helps everything whip that much better when it’s softened.
With a hand mixer or KitchenAid, combine butter and brown sugar in a large mixing bowl. Add egg and vanilla and mix fully. Add dry ingredients – flour and baking soda.
With a large wooden spoon mix in half the chocolate chips, half the marshmallows, and half the graham cracker pieces. Scoop dough onto an ungreased cookie sheet. Press the remaining s’more mix into the top of each cookie. Kids love helping with this part!
Bake at 350 degrees for 10 minutes. Cool on a wire rack before enjoying with a glass of cold milk!