Heat oven to 350℉. Lightly oil a 10-cup Bundt pan.
Using an electric mixer, beat together ¾ unsalted butter and 1 cup sugar until pale and fluffy, about 3 minutes. Beat in the 3 large eggs one at a time, then beat in the 2 teaspoons pure vanilla extract.
Beat in the 1 cup mashed very ripe bananas (batter may "break" or look grainy, this is normal). Now mix in the 1 ½ cups oat flour, ½ cup almond flour, 1 teaspoon baking powder, and ¼ teaspoon fine salt. Finally, beat in the ¼ cup plain yogurt, then fold in the 1 cup semisweet chocolate chips.
Scrape the batter into the prepared pan and let it rest while the oven heats. Place the pan on a baking sheet, then bake until a tester inserted into cake comes out clean (except for melted chocolate), about 45 minutes.
Cool the cake in the pan for about 15 minutes, then carefully unmold it onto a serving plate. Allow to cool another 15 minutes before serving.
Grease that pan. Bundt cakes are notorious for causing angst when removing the baked cake from the pan. I use plenty of butter (oil also works) to get into the nooks and crannies of the pan. You can also use baking spray.
Dairy-free. Swap the butter for melted coconut oil or non-dairy butter; trade the yogurt for non-dairy yogurt.
Spices. Make this into a fall-forward cake by adding 1 teaspoon of pumpkin pie spice, or 1 teaspoon of ground cinnamon to the batter when you add the flours.
Add nuts: Add ½ cup chopped walnuts or pecans, or use 1 cup of chopped nuts instead of the chocolate chips for a different take.