Preheat Oven: Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
Mix Dry Ingredients: In a medium bowl, whisk together flour, baking soda, salt, and cinnamon (if using).
Cream Butter and Sugars: In a large bowl, beat softened butter, granulated sugar, and brown sugar until light and fluffy.
Add Eggs and Vanilla: Beat in eggs one at a time, then add vanilla extract.
Combine Dry and Wet Ingredients: Gradually add dry ingredients to wet ingredients, mixing until just combined.
Fold in Mix-Ins: Gently fold in graham cracker pieces, mini marshmallows, and chocolate chunks.
Form Cookie Dough Balls: Scoop 1–2 tbsp of dough and roll into balls. Place on prepared baking sheets 2 inches apart.
Bake the Cookies: Bake for 10–12 minutes, until edges are lightly golden and centers are soft. Marshmallows may puff up slightly.
Cool the Cookies: Let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack.