Preheat your oven to 375°F. Line a cookie sheet with parchment paper and set it aside.
In a large mixing bowl, whisk together the flour, baking soda, and salt. Set aside.
In another large mixing bowl, beat the softened butter, granulated sugar, and brown sugar together until smooth and creamy.
Add the eggs and vanilla extract to the butter mixture, mixing until just combined.
Stir in the chocolate chips.
Add ¾ cup of the mini marshmallows (reserving the remaining ¼ cup), pulling them in half as you add them to the dough.
Roughly chop one of the chocolate bars and add it to the dough, reserving the other chocolate bar for later.
Add the crushed graham crackers to the dough and fold everything together until well combined.
Use a 1 to 1 ½ inch cookie scoop to portion out the dough onto the prepared cookie sheet, leaving plenty of space between each cookie for spreading. You may need to bake in batches.
Roughly chop the remaining chocolate bar into small and medium chunks.
Bake the cookies in the preheated oven for 8-10 minutes, or until the edges are golden brown and the centers are set.
Once baked, let the cookies cool on the baking sheet for 2-3 minutes, then carefully transfer them to a cooling rack.
While the cookies are still warm, press the reserved chocolate bar pieces and marshmallow halves into the tops of the cookies.
Enjoy your delicious S'mores Cookies!