Mash ripe bananas in a large bowl.
Whisk in melted butter, eggs, sugars, vanilla, and yogurt.
In another bowl, combine flour, cocoa, baking soda, and salt.
Stir dry ingredients into wet until just combined.
Fold in most of the chocolate chips.
Pour batter into greased and lined loaf pan.
Sprinkle remaining chips on top.
Bake at 350°F for 55-65 minutes until a toothpick shows moist crumbs.
Cool 15 minutes in pan, then transfer to a rack.