Preheat your oven to preheat to 350F. Prepare a 9×5 inch loaf pan and 6x3 inch loaf pan by lining them with parchment paper. Alternatively, you can simply grease them.
Combine the bananas in a small bowl and mash them with a fork. Set aside.
In a medium bowl, combine the all-purpose flour, cocoa powder, matcha powder, baking soda, and kosher salt. Set aside.
In a mixing bowl, combine the granulated sugar and eggs. With an electric mixer, beat on medium speed until light and fluffy, about 10 minutes. After 10 minutes, drizzle in ½ cup vegetable oil. Once the oil is fully incorporated, reduce the mixer speed to its lowest setting and add the mashed bananas and yogurt.
Sprinkle the dry ingredients over the surface of the batter. Continue mixing on low speed, and stop when the dry ingredients have just disappeared into the batter. Switch to a spatula if necessary, so the batter is not over-mixed by the mixer.
Transfer into the prepared loaf pans and smooth out the tops with a spatula.
Bake for about 50 minutes, checking at 25 minutes, as smaller loaf may be done sooner.
Meanwhile, make the icing.
Using an electric mixer, beat the heavy cream or mascarpone with the sugar until smooth and soft peaks form.
Fold in the matcha. Adjust to taste preference with more matcha and/or sugar.
Once the banana bread has cooled, slice, top with icing and enjoy!