Preheat oven to 350°F (175°C). Generously coat a muffin pan with cooking spray, but don’t use liners. Let eggs and yogurt reach room temperature. Melt coconut oil, measure, and set aside to cool. Ensure ingredients are at the same temperature to avoid clumping.
The darker the banana skin, the sweeter the banana! Remove the skin and mash with a fork or electric mixer until it resembles thick applesauce. Measure to ensure you have 1 level cup.
Add flour, cornstarch, baking soda, salt, cocoa powder, and both types of chocolate chips to a large bowl. Mix to combine. In another bowl, add egg, mashed bananas, Greek yogurt, coconut oil, vanilla extract, and brown sugar. Use a hand whisk to mix until completely smooth.
Mix the wet and dry ingredients together with a wooden spoon until just combined. Be careful not to overmix.
Divide batter evenly among the 12 muffin pan cavities. Bake for 18–23 minutes or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Cool in the muffin pan for 10 minutes, then use a table knife to gently loosen and remove the muffins. If they start to fall apart, wait another 5 minutes. Transfer to a wire rack to finish cooling. Enjoy!
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Notes
Note 1: For ultra-moist, delicious muffins, use Dutch-process cocoa powder. Regular cocoa powder makes them drier.Note 2: Use any flavor chocolate chips you like; I typically use dark chocolate with semi-sweet mini chips.Note 3: I recommend Honey Vanilla Greek yogurt (Greek Gods®) for these muffins. Avoid low-fat or non-Greek yogurt; the results aren’t the same. The creamier and thicker the yogurt, the better the muffins taste.Storage: Store in an airtight container in the fridge for up to 3 days. When ready to serve, microwave for 15–20 seconds.