Stage 1
To start, add flour, baking soda, and salt to a large mixing bowl. Mix these ingredients together and then set aside.
Next, add the sourdough discard, vanilla extract, and the egg to a bowl and mix until it forms a uniform mixture. Be careful not to overmix.
Then, add the butter, brown sugar, and white sugar to the stand mixer. Cream the butter and sugar together with the paddle attachment until you get a consistency that resembles wet sand.
Next, add the sourdough mixture to the butter mixture that is in the stand mixer bowl. Mix on a low to medium setting until uniform. Then, add in the flour mixture, a little at a time. Mix until the dough forms and is smooth and uniform.
And then, break one of the Hershey's Bar into lots of pieces (small to medium in size).
Now, remove the stand mixer bowl from the mixer and fold in the chocolate chips, the crushed graham crackers, and the Hershey's Bar pieces.
After the chocolate chips, crushed graham cracker, and broken Hershey's Bar are folded in, cover the sourdough cookie dough bowl with some plastic wrap or a tea towel and let sit in the fridge for at least an hour.
Stage 2
After at least an hour of the dough sitting in the fridge, take the cookie dough out of the fridge and line a cookie sheet with parchment paper. Preheat the oven to 350 degrees Fahrenheit. Then, scoop out ping-pong sized balls of cookie dough and put it on the cookie sheet. Spread the sourdough cookie dough balls out at least a few inches apart.
Place the cookie sheet on a rack in the middle of the oven for about 6 minutes.
Next, break apart the other two Hershey's Bar into small to medium pieces.
Once the 6 minutes are up, take the cookies out of the oven and decorate the cookies with 2-3 pieces each of Hershey's Chocolate Bar. Then, place the cookies back into the oven for about 4 more minutes.
After about 10 minutes, take the cookies out of the oven and add a few pieces of mini marshmallow to each cookie.
Let the cookies sit on the cookie sheet for at least 10 minutes before removing from the pan. You'll know that the cookies are done when the bottom of the cookies are golden brown.