1 1/2 cups (180g) unbleached all-purpose flour
1/2 cup (43g) unsweetened cocoa (regular or Dutch-process)
3/4 cup (140g) dark brown sugar
3/4 teaspoon baking soda
3/4 teaspoon sea salt or kosher salt
1/3 cup (80ml) extra-virgin olive oil
2 large eggs, lightly beaten
1 1/2 cups (350g) ultra ripe bananas (from about 3 large bananas), mashed with a fork into a smooth puree
1/4 cup (60g) sour cream or plain Greek yogurt (full fat is best)
1 1/2 teaspoons vanilla extract
1 cup (113g) coarsely chopped dark chocolate (equals a 4-ounce bar), or an equal amount of dark chocolate chips
1/2 cup (65g) chopped pecans or walnuts (optional)