Prep the pan and oven: Heat the oven to 350°F (175°C). Line a 9x5-inch loaf pan with parchment, leaving overhang for easy lifting. Lightly grease.
Mix wet ingredients: In a large bowl, mash the bananas until mostly smooth.
Whisk in eggs, yogurt, oil, brown sugar, and vanilla until combined.
Combine dry ingredients: In a separate bowl, whisk flour, baking soda, baking powder, salt, and optional spices.
Bring the batter together: Add dry ingredients to wet and stir gently until just combined. Fold in the dark chocolate chunks. Do not overmix.
Make the tahini swirl: In a small bowl, whisk tahini with maple syrup or honey until glossy and slightly loosened.
If very thick, add 1–2 teaspoons warm water.
Layer and swirl: Pour half the batter into the pan. Dollop half the tahini over it. Add the remaining batter, then the rest of the tahini.
Use a butter knife to gently swirl—2–3 passes is enough.
Top and bake: Sprinkle a few extra chocolate chunks on top. Bake 55–65 minutes, until a toothpick inserted in the center comes out with a few moist crumbs (melted chocolate is fine).
Cool: Let the loaf cool in the pan for 15 minutes, then lift out and cool fully on a rack before slicing. This helps set the crumb and swirl.