Preheat your oven to 350°F (175°C) and prepare a 9-by-5-inch loaf pan by greasing with butter or lining with parchment paper.

In a large mixing bowl, whisk together flour, light brown sugar, baking soda, kosher salt, ground cinnamon, and ground allspice. Toss in chopped dates to coat them with flour.

In a separate bowl, mash the ripe bananas, then add yogurt or sour cream, eggs, melted butter, and vanilla extract. Mix until combined.

Gently fold the banana mixture into the dry ingredients until just combined, leaving a few floury streaks.

Pour the batter into the prepared loaf pan and level the top. Sprinkle dark brown sugar on top.

Bake in the preheated oven for 45 to 55 minutes, or up to 65 minutes for stoneware, until golden brown and a toothpick comes out clean.

Cool in the pan for 5 to 10 minutes, then turn out onto a wire rack to cool completely before slicing.