Heat the oven to 350F. Spread the shredded coconut one layer deep on a sheet pan and toast it while the oven comes up, 8 to 10 minutes, stirring at 4 minutes and again at 7. Pull it at pale gold, since it browns fully in the last ninety seconds, and set it aside to cool.

Butter a 9x5-inch loaf pan and line it with a parchment sling. Melt the chopped chocolate in a bowl set over a pan of barely simmering water, then take it off and let it cool until it is warm rather than hot.

Sift the flour, cocoa powder, baking powder, baking soda, salt and cinnamon into a bowl and set it aside.

Beat the eggs and granulated sugar on medium speed until pale and thick, about 3 minutes. Add the yogurt, oil and mashed bananas and mix until combined. Both the eggs and the yogurt need to be at room temperature or the chocolate will seize into specks in the next step.

With the mixer on low, drizzle in the melted chocolate, using the cup the oil was measured in so none of it clings. Scrape the sides and base of the bowl, add the dry ingredients and mix only until they disappear, then fold in the cooled coconut by hand.

Scrape the batter into the pan and level the top. Scatter the turbinado sugar evenly over it.

Bake 60 to 70 minutes. Color is no guide on a cocoa loaf, so test with a thermometer: the center should read 200F to 205F. A skewer should come out with moist crumbs, though a smear of melted chocolate is not the same as raw batter.

Cool the loaf 10 minutes in the pan, then run a knife around the ends and lift it out by the parchment onto a wire rack. Let it cool completely before slicing or the crumb tears.

Wrap it once it is fully cold, never while warm, since trapped steam turns the turbinado crust tacky. It keeps 3 days at room temperature and is at its best on day two.