01 -
Preheat the oven to 375° F. Line two baking sheets with parchment paper.
02 -
Combine softened butter, light brown sugar, and granulated sugar in a large mixing bowl. Beat for 2-3 minutes until the mixture is light and creamy.
03 -
Add eggs and vanilla extract to the mixture, beating well until fully incorporated.
04 -
Add all-purpose flour, cornstarch, baking soda, and salt. Mix just until combined, avoiding overmixing.
05 -
Gently fold in 1 1/2 cups graham cracker pieces, 1 1/2 cups mini marshmallows, milk chocolate chips, and semisweet chocolate chips, distributing them evenly throughout the dough.
06 -
Scoop dough in 2–3 tablespoon portions onto the prepared baking sheets, allowing space between each for spreading.
07 -
Bake in the oven for 10 minutes or until almost set.
08 -
Remove the baking sheets from the oven. Gently press 4–5 additional mini marshmallows, a few more pieces of graham cracker, and Hershey bar segments onto the top of each cookie.
09 -
Return cookies to the oven and bake for 1–2 more minutes until fully baked. For toasted marshmallow tops, briefly switch the oven to broil, watching carefully to avoid burning the marshmallows.
10 -
Allow cookies to cool on the pan for 2–3 minutes, then transfer to a wire rack to finish cooling. Store cooled cookies in an airtight container at room temperature for up to 5 days.