225 g (16 tablespoons) butter, at room temperature
250 g (1 1/4 cup) granulated sugar
150 g (2⁄3 cup tightly packed) light brown sugar
2 g (1/2 tsp) vanilla extract
240 g (1 1/2 cups) all purpose flour
2 g (1/2 tsp) baking powder
1.5 g (1/4 tsp) baking soda
5 g (1 1/4 tsp) kosher salt
125 g (2/3 cup) mini chocolate chips
80 g (2 cup) broken graham crackers - about 5 graham crackers
65 g (1 1/4 cup) marshmallows
Combine the butter and sugars in the bowl of a stand mixer fitted with the paddle attachment and cream together on medium-high for 2 to 3 minutes. Scrape down the sides of the bowl, add the egg and vanilla, and beat for 7 to 8 minutes.
Reduce the speed to low and add the flour, baking powder, baking soda, and salt. Mix just until the dough comes together, no longer than 1 minute. (Do not walk away from the machine during this step, or you will risk over mixing the dough.) Scrape down the sides of the bowl with a spatula.
Still on low speed, add the chocolate chips and broken graham crackers, mix just until incorporated, about 30 seconds. Add the marshmallows and mix until just incorporated. Be careful not to over mix or the marshmallows will become over incorporated into the dough and you’ll lose that ooze!
Using a 2 3/4 oz ice cream scoop (or a 1/3 cup measure), portion out the dough onto a parchment-lined sheet pan. Pat the tops of the cookie dough domes flat. Wrap the sheet pan tightly in plastic wrap and refrigerate for at least 1 hour, or up to 1 week. Do not bake your cookies from room temperature— they will not bake properly.
Heat the oven to 350°f, or 325 if using convection.
Arrange the chilled dough a minimum of 4 inches apart on parchment- or silpat-lined sheet pans. Bake for 18 minutes. The cookies will puff, crackle, and spread. after 18 minutes, they should be very faintly browned on the edges yet still bright yellow in the center. Give them an extra minute or so if that’s not the case.
Cool the cookies completely on the sheet pans before transferring to a plate or an airtight container for storage. At room temp, cookies will keep fresh for 5 days; in the freezer, they will keep for 1 month.