Preheat oven to 350 F. Grease a cooking sheet or add parchment paper to the sheet if necessary.
Add your softened butter and sugars to a mixing bowl. Beat until a creamy texture. (pro tip: if you're butter is cold, defrost in microwave for 1 minute--but don't let it melt!!)
Next, add the egg and vanilla and mix well.
Then add baking powder and salt. Crumble your graham crackers and throw them into the mixing bowl in "stir" mode. (make sure you are scraping sides occasionally to be sure things are mixing well!).
Slowly add the flour into the mixture in "stir" mode (or, you're slowest mixing mode on your mixer). Add the optional chococlate chips and fold in with a rubber spatula or spoon.
If you have time, let the dough chill for 30 -60 minutes in the fridge. This improves the texture of the cookie but isn't necessary. **if you accidentally melted your butter- you need to chill your dough, though.
Form 2 tbsp cookies and lay on sheet. Bake for 12 minutes at 350 F. Remove from oven and immediately add a square of chocolate and marshmallow. Add back into the oven for 1 minute so that they get nice and melty.
Remove from oven and use spatula to gently press down on the marshmallow if desired, for looks. Let cool and enjoy! Makes about 12 cookies.
Notes
Let cool completely and store in airtight container for up to 4 days. Nutrition information is an estimate.