Prep your pans and oven. Line two baking sheets with parchment paper. Preheat oven to 350°F (175°C). This helps the cookies bake evenly and release cleanly.

Mix dry ingredients. In a bowl, whisk flour, baking soda, and salt until combined. Set aside.

Cream the butter and sugars. In a large bowl, beat softened butter, brown sugar, and granulated sugar on medium speed for 2–3 minutes, until light and slightly fluffy. This step creates air for a softer cookie.

Add eggs and vanilla. Beat in the egg and egg yolk, then vanilla, scraping the bowl once. Mix just until smooth.

Combine wet and dry. Add the dry mixture to the wet on low speed. Mix until a few flour streaks remain. Don’t overmix.

Fold in the good stuff. With a spatula, gently fold in chocolate chips, chocolate chunks, and graham cracker pieces. Reserve a small handful of each for topping. Fold in 3/4 cup of the mini marshmallows, saving the rest for the tops so they toast instead of melting inside.

Chill briefly. Cover the bowl and chill the dough for 20–30 minutes. This keeps the cookies thick and prevents excess spread.

Scoop and top. Scoop dough into balls about 2 tablespoons each (a medium cookie scoop). Press a few reserved chocolate pieces, graham bits, and 2–3 mini marshmallows onto the tops. This gives that classic s’mores look and perfect toasty spots.

Bake. Place 2 inches apart on prepared sheets and bake 9–12 minutes, until edges are set and lightly golden but centers look slightly underdone. For extra gooey, pull them around 10 minutes.

Optional torch or broil. For deeper marshmallow toast, you can briefly broil for 10–20 seconds, watching closely, or kiss the tops with a kitchen torch. Don’t walk away.

Finish and set. Immediately sprinkle with a pinch of flaky sea salt and press on an extra square of chocolate if you like. Let cookies cool on the sheet for 5–10 minutes to set before moving to a rack.