Preheat your oven to 375°F (190°C) and prepare an 8.5 x 4.5-inch loaf pan by greasing or lining it with parchment paper.

Spread the saikyo miso paste onto a silicon mat, about ¼ cm (1/6 inch) thick. Bake it in the preheated oven for 8-10 minutes, or until the surface is nicely burnt and aromatic.

While the miso bakes, prepare the brown butter. In a small saucepan over medium heat, melt the vegan butter. Once it begins to foam, swirl the pan and continue cooking until it turns golden brown and fragrant.

Pour the butter into a bowl, ensuring to measure it out (aim for about 85-95 g). Add the melted coconut oil to make a total of 1/2 cup (114 g).

In a separate bowl, sift together the all-purpose flour, baking powder, and baking soda. Then whisk in the spelt flour until combined.

Remove the burnt miso from the oven and lower the temperature to 350°F (175°C). Scrape the miso into the bowl with the browned butter.

Mash one banana (approximately 170 g) and add it along with the non-dairy sour cream, apple cider vinegar, and vanilla extract to the bowl. Use an immersion blender to blend everything until smooth.

Mash the remaining bananas well and add them to the mixture. Ensure there are no large chunks if you prefer a smooth texture in your bread.

Stir in the cane sugar, brown sugar, cinnamon, and nutmeg until the mixture is well combined.

Fold in the dry ingredients, being careful not to overmix. The batter should be just combined with no visible flour.

Pour the batter into the prepared loaf pan. Tap it on the counter three times to remove excess air bubbles. If you like, sprinkle your chosen toppings on top at this stage.

Bake for 65-75 minutes. The bread will darken considerably but should not taste burnt.

Once baked, remove the loaf from the pan and cool on a wire rack for at least one hour.

While you can serve it immediately, the flavor deepens if you let it rest overnight. Wrap the loaf with cling wrap and allow it to sit.