Preheat the oven to 425 degrees F (220 degrees C) and line a muffin tin with parchment cups. You can also make your own by cutting squares of parchment paper, two per muffin, and pressing them into the molds.
In a medium bowl, whisk together the flour, cocoa powders, espresso powder, salt, baking powder, and baking soda.
In a separate large bowl, whisk together the sugars, oil, yogurt, and tahini.
Add in the eggs and vanilla, and whisk until fully combined.
Whisk in the melted chocolate until fully combined.
Fold the dry ingredients into the wet until just combined.
Lastly, fold in the chopped chocolate.
Use a 3 tablespoon cookie scoop to divide the batter between the muffins cups. If using your own DIY parchment liners, it's easier to hold it in your hand and fill it using the cookie scoop, then place it back in the muffin pan.
Top the muffins with more chopped chocolate if desired, then bake the muffins for 5 minutes.
After 5 minutes, lower the oven temperature to 350 degrees F (180 degrees C), and bake for another 10-12 minutes.
Allow the muffins to cool in the pan for a couple minutes, then transfer to a wire rack to cool completely.