Preheat the oven to 350 degrees F. Prepare a 9x13 baking pan by lining it with a sheet of parchment paper with 'handles' extending on both sides. (Watch the video to see this.)
In the bowl of a stand mixer or a large bowl with a hand mixer, cream the butter and sugars together until creamy and smooth.
Add in the eggs, one at a time, and vanilla extract. Mix until combined.
In another large bowl, combine graham cracker crumbs, flour, baking soda, and salt; set aside.
Slowly add the dry ingredients to the wet ingredients and mix until just combined.
Press the dough into the lined baking pan.
Bake for 12-14 minutes, or until the middle is just barely set. Remove from oven.
Melt about ⅔ of the chocolate chips in the microwave on 30-second burst. Stir between bursts. Spread the melted chocolate over the cookie base and sprinkle on the mini marshmallows. Return to the oven for 3-5 minutes. Remove from oven.
If you want more toasty marshmallows, toast them with a kitchen torch.
Melt the remaining chocolate chips in the microwave on 30-second bursts. Put the chocolate into a piping bag or sandwich bag. Snip off the tip of the bag and drizzle over the top of the smores bars. You can also drizzle using a spoon or spatula.
Once cooled, cut into bars using a plastic scraper or a knife (the marshmallows don't stick to plastic cutters!) and serve. Store in an airtight container for up to 5-7 days.