Design Eat Repeat

0 Preheat oven to 350°F - this is important! You want to give your oven at least 20 minutes to heat up EVEN if it beeps and tells you it’s preheated after 5 minutes (ovens lie!).
1 In a large mixing bowl, use an electric mixer to beat melted butter ([adjustable]½ cup, i.e. 1 stick[/adjustable]) and ripe bananas (1½ cups, i.e. about 3 large bananas) until mashed & smooth. You want to make sure you break up any large pieces or you will have large pieces of banana in your bread and it can cause it to bake weird.
2 Add light brown sugar ([adjustable]½[/adjustable] cup), and granulated sugar ([adjustable]½[/adjustable] cup), then mix until just combined. You don't want to beat this longer than it takes to incorporate.
3 Add in the eggs ([adjustable]2[/adjustable] large), sour cream ([adjustable]½[/adjustable] cup), and vanilla extract ([adjustable]2[/adjustable] teaspoons) then stir until just combined. Once mixed, add in the baking soda ([adjustable]1 [/adjustable]teaspoon), and baking powder ([adjustable]½[/adjustable] teaspoon), and salt ([adjustable]½[/adjustable] teaspoon) then mix again until just combined.
4 Mix this step with a spatula (not the mixer!).Lastly, mix in cornstarch ([adjustable]1 tablespoon), cocoa powder (½ cup), and all-purpose flour (1 cup)[/adjustable] and stir until just combined. Do not mix this for any longer than it takes for the flour to disappear or it will become dense and chewy. Do not overmix!
9 In a small bowl, mix chocolate chips [adjustable](1 ¼ cup) with extra flour (2 tablespoons)[/adjustable]. This will help the chocolate chips not sink as much in the batter.
10 Mix 1 cup of the chocolate chips (not the whole amount!) into the batter (we're reserving the remaining [adjustable]¼[/adjustable] cups for sprinkling on top).
5 Grease and line a 9" metal loaf pan with parchment paper, leaving a ½" overhang on all sides to hold the loaf if it starts to rise out of the pan.Fill pan ¾ full (you can usually fill up heavy batters like this almost all the way, just being sure to leave about ½″ at the top without having it rise over). Note: Because there are varying size of “standard” loaf pans (some are wider than others and therefore fit more), you may end up with a little extra batter. See notes below for baking times for extra muffins.
8 Sprinkle the remaining [adjustable]¼[/adjustable] cup of flour-covered chocolate chips on top.
6 (Read this step carefully!) Bake at 350°F for 60-75 minutes on the bottom or middle rack of your oven, until a toothpick comes out clean (minus the gooey chocolate chips!) or the internal temperature reaches 200°F. After 30 minutes of it baking, gently cover the top of your loaf with foil to prevent the top from browning. When baking, place your loaf near the bottom/middle of oven. You do not want it too close to the top or the top will brown faster than the inside can cook.
7 Test doneness by sliding a toothpick or skewer into the center (or using an internal thermometer) while it's still in the oven. If it comes out clean (or just with a crumb or two, minus the gooey chocolate chips) it's ready.Once baked, you should ideally allow banana bread to cool in the pan for about an hour to allow it to set and cool. If not eating right away, cover with foil and let it completely cool before putting in a ziploc bag. Wrapping it in plastic too soon will trap the steam and could make your bread mushy. See notes below for storage instructions.