Dry Mix

• 1 cup buckwheat flour
• 1½ cups all-purpose flour
• ¼ cup plus 2 tablespoons unsweetened natural cocoa powder
• 2 teaspoons baking powder
• 1 teaspoon kosher salt
• ½ teaspoon baking soda

Wet Mix

• 3 ounces (¾ stick) cold unsalted butter, cut into ½ inch pieces
• ¼ cup dark brown sugar
• ¼ cup sugar
• 2 eggs
• ½ cup plain yogurt
• 2 cups Hachiya persimmon pulp, from 2 large or 4 small ripe persimmons
• 4 ounces bittersweet chocolate, 50 to 60 percent cacao, cut into roughly ¼-inch pieces

1. Preheat the oven to 350°F. Rub muffin tins with a ⅓-cup capacity with butter. Sift the dry ingredients into a large bowl, pouring back into the bowl any bits of grain or other ingredients that may remain in the sifter.
2. Add the butter and the sugars to the bowl of a standing mixer. Attach the paddle, mix on low speed until the ingredients are combined, then turn to high speed and cream until the butter and sugars are light and creamy, about 3 minutes. Using a spatula, scrape down the sides and the bottom of the bowl. Add the eggs and mix on medium speed for about 1 minute, until thoroughly combined. Add the yogurt and mix until combined. Again, scrape down the sides of the bowl.
3. Add the dry ingredients to the bowl and mix on low speed until combined. Remove the bowl from the mixer, add the persimmon pulp and the chopped chocolate, and fold them gently into the batter by hand. Scrape down the sides and the bottom of the bowl to evenly combine the ingredients.
4. Scoop the batter into 8 muffin cups, using a spoon or an ice cream scoop. The batter should be slightly mounded above the edge. There will be a few gelatinous pieces of persimmon in the batter; if you can, take them from the batter and drape or tuck them into the tops of the muffins for a pretty finish.
5. Bake for 33 to 37 minutes, rotating the pans halfway through. As the muffins are dark, it is hard to tell when they are ready to come out. Test the muffin like you would a cake, pressing into its top to see how much give there is; it should spring back lightly. Take the tins out of the oven, twist each muffin out, and place it on its side in the cup to cool. This ensures that the muffin stays crusty instead of getting soggy. These muffins are best eaten warm from the oven or later that same day. They can also be kept in an airtight container for up to 2 days, or frozen and reheated.