Grease the inside of a 6-quart slow cooker with butter or non-stick spray. Line with parchment paper, leaving an overhang for easy removal, and grease the parchment.

In a large mixing bowl, thoroughly mash the overly ripe bananas until smooth. Aim for about 1 cup.

Pour the melted butter over the mashed bananas. Stir in the eggs, vanilla extract, and the sour cream or Greek yogurt. Mix until just combined.

In a medium bowl, whisk together the flour, both white and brown sugar, baking soda, baking powder, and salt. Whisking ensures the leaveners are evenly distributed.

Slowly add the dry ingredients to the wet ingredients. Mix gently with a spatula only until the flour streaks have almost disappeared. Overmixing is the enemy of a super moist chocolate chip banana bread, as it develops gluten and creates toughness.

Gently fold in 3/4 cup of the chocolate chips. Reserve the remaining 1/4 cup for sprinkling on top.

Pour the batter into your prepared slow cooker. Sprinkle the remaining chocolate chips over the top. Smooth the top lightly.

Cover the slow cooker and cook on HIGH for 2-2.5 hours or until a toothpick inserted into the center comes out clean or with a few moist crumbs attached (not wet batter). Avoid opening the lid frequently to maintain even cooking.

Once done, turn off the slow cooker. Let the bread cool completely in the slow cooker with the lid off for 1 hour to set. Then, use the parchment overhang to lift it out and transfer to a wire rack for further cooling.