Put the semi-sweet chocolate and oil in a large microwave-safe bowl and microwave on high for 30 seconds and then stir. Continue to microwave in 10 second increments until the chocolate is melted. If you don’t have a microwave, a double boiler will work just fine. Set aside to cool a beat.
Once the chocolate mixture is cooled a bit, whisk the eggs into the chocolate mixture. Whisk in the vanilla, brown sugar and granulated sugar. This mixture will be thick…don’t panic. 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. Mix until barely combined. Add the mini marshmallows, chocolate + walnuts (if you’re using them) and give the cookie dough a couple more stirs. Chill cookie dough for 30 minutes in the fridge. This will make it easier to roll into balls.
Preheat your oven to 375 degrees F and have a rack in the top third of the oven…this is where you’ll bake your cookies. Line your cookie sheets with parchment paper.
Gently roll together 2 tablespoons of dough and allow at least two inches between the dough balls. Try to make them as spherical as possible. They will spread a touch while baking. If you have the time, I highly recommend either freezing these dough balls for 5 minutes or placing them in the fridge for 20 minutes prior to baking. This will keep cookie spread to a minimum. You know how I like girth in a cookie. Bake for 11 minutes. You want to slightly undercook these…they might even look underdone a bit. That’s perfect. Allow the cookies to cool on the sheet for 5-10 minutes, or until they come off easily.
Grab us two martinis and let’s eat some chocolate marshmallow cookies.