Preheat the oven to 350 F. Butter muffin pans (I use a butter baking spray, because it is incredibly easy to use)
In a bowl, mix the flour, cocoa powder, salt, and baking soda. Set aside.
In another bowl, whisk the egg. Add butter, vanilla, buttermilk and tahini. Mix. Mash the bananas into the liquid mixture.
Add the flour mixture to the bowl of liquid and gently fold the ingredients together. Add chocolate chips.
Scoop the batter into the butter muffin pans. Sprinkle muffins with sesame seeds. Bake muffins for 12-15 minutes. Remove from the oven and cool on a baking rack.
I slightly undercooked the banana muffins; it gave them a fudgy moist interior. You can't really taste the tahini. In the future, I'll play around with adding more to really get the roasted sesame flavor.