Melt the 8-ounces of chocolate + oil in the microwave (I usually do 1 minute on High, but microwaves are funky so keep an eye on things) in a large microwave-safe bowl or in a double boiler. Stir the chocolate to get rid of any chunks. Sometimes it will look chunky, but if you give it 20 or so stirs with a wooden spoon, you’ll get rid of all of the chunks without overheating (scalding) it.
In a separate bowl, beat together 3 eggs. Whisk the beaten eggs into the chocolate mixture. Whisk in the vanilla extract, brown and granulated sugar. Set aside.
In another bowl whisk together both flours, cocoa powder, baking powder and soda and salt. Pour the flour mixture into the chocolate mixture. Add the chopped chocolate chunks. Mix until just combined. Chill cookie dough for 30 minutes in the fridge.
Preheat your oven to 375 degrees F. Line your cookie sheets with parchment paper.
Roll together 2 tablespoons of dough and allow at least two inches between the dough balls. Try to make them as spherical as possible and equal in size so they will pair up nicely when schmooshing the marshmallows in between them. Only put 9 cookie balls on a standard-size cookie sheet. They will spread a bit while baking.
If you have the time, I highly recommend either freezing these dough balls for 10 minutes or placing them in the fridge for 20 minutes. This will keep cookie spread to a minimum. You know how I like girth in a cookie.
Cook for 11 minutes. You want to slightly undercook these. Allow the cookies to cool on the sheet for 5-10 minutes, or until they come off easily.