Preheat oven to 350°F (175°C) and line baking sheets with parchment paper or silicone mats. Ensure butter is softened to room temperature.
In a medium bowl, whisk together flour, baking soda, baking powder, salt, pumpkin pie spice, and cinnamon until evenly combined. Set aside.
Beat softened butter with brown sugar and granulated sugar on medium-high speed for 2–3 minutes until light, fluffy, and pale. Scrape down the bowl as needed.
Mix in the pumpkin puree, egg, and vanilla extract until smooth and uniform. The batter may look slightly curdled — this is normal.
Add the flour mixture in three batches on low speed, mixing just until no flour streaks remain. Scrape the bowl and give a final gentle hand stir — do not overmix.
Using a rubber spatula, gently fold in the dark chocolate chunks until evenly distributed. The dough will be soft and slightly sticky.
Scoop 2-tablespoon portions of dough onto prepared baking sheets, spacing them 2 inches apart. Gently flatten each ball slightly.
Bake for 10–12 minutes, until edges are set but centers still look slightly underdone. Remove from oven and immediately press one marshmallow on top of each hot cookie.
Using a kitchen torch, toast each marshmallow until golden brown; alternatively, broil on the top rack for 30–60 seconds, watching closely to prevent burning.
While marshmallows are still warm, press graham cracker pieces into each and sprinkle with mini chocolate chips if desired. Cool on the sheet for 5 minutes, then transfer to a wire rack.