Preheat oven to 350°F/177°C.
Line an 8" by 4" loaf pan with parchment paper.
In a large bowl, use a fork to mash the banana.
Add in the eggs, avocado oil and vanilla extract and give it a whisk.
Stir in the yogurt/sour cream, sugar, and sift in the cinnamon, baking soda and baking powder.
Add in the all-purpose and cake flour and use a spatula to fold until just incorporated.
Lastly, fold in the chocolate chunks.
Transfer the mixture to a prepared loaf pan. Give the pan a few taps to release any trapped air bubbles.
Bake for 60-65 minutes at 350°F/177°C, or until a toothpick inserted comes out clean or with slight crumbs clinging to it.
If the top appears to brown too quickly, cover with aluminum foil. Note 1: Depending on your oven, it may require more or less baking time. Note 2: If you stick the toothpick into chocolate or a chunk of banana, it could "appear" wet.
Remove from the baking pan and let completely cool on a wire rack.
Slice and serve.