Step 1: Make the graham cracker crumbs:

Place the graham crackers in the bowl of a food processor. Process in pulses until the crackers are completely broken down into fine crumbs. Aim for a consistent texture, similar to coarse sand.

Alternatively: If you don't have a food processor, place the graham crackers in a zip-top plastic bag. Seal the bag tightly, removing as much air as possible. Use a rolling pin to crush the crackers into fine crumbs. This method might require a bit more elbow grease, but it works just as well! Ensure there aren't any large pieces of graham cracker remaining.

Step 2: Whisk the dry ingredients:

In a medium-sized mixing bowl, combine the graham cracker crumbs, all-purpose flour, salt, and baking soda.

Use a whisk to thoroughly combine all the dry ingredients. This ensures that the baking soda and salt are evenly distributed throughout the flour mixture, which is crucial for proper leavening and flavor balance. Whisking also helps to aerate the flour, resulting in a lighter, more tender cookie.

Step 3: Beat the butter and sugars:

In a large mixing bowl (or the bowl of a stand mixer fitted with the beater attachment), cream together the softened butter, granulated sugar, and packed brown sugar.

Beat on medium speed until the mixture is light, fluffy, and well combined, about 3 to 5 minutes. This process is essential for creating a light and airy cookie base. The creaming action incorporates air into the butter, which contributes to the cookie's texture. Make sure the butter is truly softened, but not melted. If it's too cold, it won't cream properly; if it's melted, the cookies will spread too much.

Pick out any large clumps or pebbles of hard brown sugar that you see. These can prevent the sugar from dissolving properly and affect the texture of the cookies. Scrape down the sides of the bowl and the beater occasionally to ensure that everything is evenly incorporated.

Step 4: Mix in the eggs and vanilla:

Add the two large eggs, one at a time, to the butter-sugar mixture, beating well after each addition.

Continue to beat at medium speed until the mixture is smooth and creamy, with no visible streaks of egg yolk. This step helps to emulsify the mixture and create a stable base for the cookies. Scrape down the sides of the bowl and the beaters after each egg addition to ensure even incorporation.

Stir in the vanilla extract. The vanilla enhances the overall flavor of the cookies and complements the chocolate and marshmallow flavors.

Step 5: Mix in the dry ingredients:

Gradually add the graham cracker and flour mixture to the wet ingredients, beating on low speed until just combined.

Be careful not to overmix the dough. Overmixing can develop the gluten in the flour, resulting in tough cookies. Mix until the dry ingredients are just incorporated, with no visible streaks of flour remaining.

Step 6: Mix in the chocolate:

Add the chopped chocolate or chocolate chips to the dough and mix on low speed until evenly distributed.

Use a variety of chocolate types, such as milk chocolate, dark chocolate, or semi-sweet chocolate, to add depth and complexity to the flavor. You can also use chocolate chunks for a more rustic look and a richer chocolate experience.

Step 7: Chill the dough:

Cover the bowl tightly with plastic wrap or transfer the dough to an airtight container.

Refrigerate the dough for at least 30 minutes, or up to 3 days. Chilling the dough allows the gluten to relax, which helps to prevent the cookies from spreading too much during baking. It also allows the flavors to meld together, resulting in a more flavorful cookie. For best results, chill for at least 2 hours.

Alternatively: You can freeze the dough in individual scoops for up to 3 months. This is a great way to have cookie dough on hand for whenever you're craving a sweet treat. To bake from frozen, simply thaw the dough in the refrigerator for a few hours before baking.

Step 8: Preheat the oven and prepare baking sheets:

Preheat your oven to 375°F (190°C).

Place a rack in the middle of the oven. Line two baking sheets with silicone baking mats or parchment paper. This prevents the cookies from sticking to the baking sheets and makes for easy cleanup.

Step 9: Scoop the dough:

Use a medium cookie scoop (or a well-mounded tablespoon measure) to scoop the dough onto the prepared baking sheets, spacing the cookies about 2 inches apart.

This allows the cookies to spread evenly without touching each other.

Step 10: Bake the cookies:

Bake the cookies for 8 to 10 minutes, or until the edges are lightly golden brown and the centers are still slightly soft.

Remove the baking sheets from the oven.

Step 11: Add the marshmallows:

Gently press 3 to 4 mini marshmallows into the tops of each cookie.

Return the cookies to the oven and bake for another 2 to 3 minutes, or until the marshmallows are puffed and lightly golden brown. Keep a close eye on the cookies during this step, as the marshmallows can burn easily.

Step 12: Cool the cookies:

Remove the baking sheets from the oven and let the cookies cool on the baking sheets for a few minutes before transferring them to a wire rack to cool completely.

This allows the cookies to firm up slightly and prevents them from breaking when you transfer them.

Step 13: Enjoy!

Serve the cookies warm or at room temperature.

Store cooled cookies in an airtight container at room temperature for up to 3 days. The marshmallows may become slightly sticky after a day or two.