In a medium sauce pan, add in the butter, place over medium heat and melt. Peel approximately 3 bananas (325 grams peeled) and cut in half lengthwise and crosswise. Pour in the brown sugar, cinnamon, and the bananas into the pan. Heat over low heat, stirring regularly until the bananas start to soften and become fragrant.
Once a bit soft and saucy, remove it from the heat and pour into a heat safe mixing bowl. Set aside to cool.
Chop up your choice of chocolate and set aside. If adding nuts, this is the perfect time to toast and chop them up. Use 150 -200 grams of walnuts or pecans.
Once the banana mixture has cooled, pour in white sugar, salt, vanilla, yogurt, oil, and eggs. Whisk to combine. An electric mixer is great here but a regular manual whisk will work too just make sure everything is fully combined.
In a separate bowl, whisk the flour and baking soda together.
Pour the dry ingredients into the wet. Before mixing together, peel and chop the last banana into 1/2" chunks. Add the chocolate and banana chunks (and nuts if adding) on top of the dry ingredients.
Use a rubber spatula to fold the dry ingredients and add-ins into the wet ingredients. Mix until just combined.