Preheat the oven to 350°F and line baking sheets with parchment paper.
In a large bowl, whisk the butter, granulated sugar, and brown sugar together until the mixture light and fluffy (about 2 to 3 minutes).
Add the egg and vanilla extract and whisk until the ingredients are well combined.
In a separate bowl, whisk together the flour, ground cinnamon, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing after each addition until the ingredients are just combined.
Add the chocolate chips, crushed graham crackers, crushed pretzels (optional), and mini marshmallows to the bowl, and use a spatula to gently fold them into the cookie dough mixture.
Use a cookie scoop or a tablespoon to portion out the s’mores cookie dough (about 1 ½ tablespoons of dough per cookie) onto the prepared baking sheets, leaving about 2 inches of space between each cookie.
Gently press a few extra mini marshmallows and pieces of Hershey’s chocolate onto the tops of the cookie dough balls. This gives them a gooey, s’mores like texture and look when baked.
Bake the s’mores cookies for 8 to 10 minutes, or until the edges are light golden brown. The centers may look slightly underbaked.
Let the cookies cool on the baking sheet for 5 minutes, and then use a cookie spatula to transfer them to a wire rack to cool.
Enjoy the cookies slightly warm for that classic gooey s’mores vibe.