Cocoa-nana Bread

We had this Cocoa-nana Bread from Dorie Greenspan's Baking cookbook the other morning, and it was yummy!  The calories per slice for 12 slices are 327 and we gave this a 9.  I like how easy it is, and the boys love the flavor.  It is more cocoa than banana, but it's still yummy!  Here's the recipe:
2 c flour
1 c cocoa powder
1 1/2 t baking powder
1/2 t salt
1/4 t baking soda
1 stick unsalted butter at room temperature
3/4 c sugar
1/2 c packed brown sugar
2 large eggs
2 ripe bananas, mashed
3/4 c buttermilk
1/2 c chocolate chips

Preheat oven to 350.  Butter a 9x5 loaf pan and place it on an insulated baking sheet.
Sift together the flour, cocoa, baking powder, salt, and baking soda.
Working with a stand mixer, beat the butter at medium speed for about 1 minute, until softened.  Add the sugars and beat for 2 minutes more.  Add the eggs, beating after each addition.  Reduce the mixer speed to low and add in the mashed bananas.  Add the dry ingredients in 3 additions, mixing only until they disappear into the batter.  Add the buttermilk, mixing until it is incorporated.  Add in the chocolate chips with a spoon.  Scrape batter into prepared pan.  Bake for 30 minutes.  Cover loosely with foil to keep the top from getting too dark, then bake for another 40-45 minutes (I had to cook mine for 15 minutes longer than that, so 90 minutes in all) until inserted knife comes out cleanly.  Transfer the pan to a rack and cool for 20 minutes.  Remove from pan and cool completely.