• Whisk together the all-purpose flour, baking powder, baking soda, and salt in a medium bowl. Set aside. 220 g all-purpose flour, 3/4 tsp baking soda, 1/2 tsp baking powder, 1/2 tsp salt
• Add hot water to a large mixing bowl. Whisk in the cocoa powder and espresso powder. 120 g just boiled water, 40 g cocoa powder, 1 teaspoon instant espresso powder
• Add sugar, sour cream, oil, sourdough, eggs, and vanilla. Whisk until well combined. 200 g granulated sugar, 180 g sour cream , 105 g vegetable oil , 100 g sourdough discard starter, 2 large eggs, 1 teaspoon vanilla extract
• Add the flour mixture and the chocolate chunks to the wet ingredients and mix in until just combined. 160 g chocolate chunks
• The muffins can be baked right away or cold-fermented overnight.
• Cold-fermenting - Cover the bowl tightly and place it in the refrigerator for up to 16 hours. Cold fermenting allows the flour to absorb more moisture from the batter, which leads to a more moist crumb. Additionally, slow fermentation helps break down the proteins in the flour.

Baking

• Preheat the oven to 425°F (220°C) and grease or line the muffin tin.
• Use an ice cream scoop to divide the muffin batter evenly between the lined muffin tin. They will be full.
• Bake for 5 minutes in the preheated oven, then turn the oven down to 350°F (180°C) and bake for 18-20 minutes more until the muffin tops spring back when pressed.
• Let the baked muffins cool in the pan for 5 minutes before removing them and placing them on a wire rack to cool further.