Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 9x5 inch loaf pan, or line with parchment paper leaving an overhang on the sides.
Step 2: In a large bowl, whisk together the all-purpose flour, light brown sugar, cocoa powder, espresso powder, baking powder, and kosher salt until well combined.
Step 3: In a separate medium bowl, whisk together the whole milk, large egg, 2 tablespoons melted unsalted butter, and vanilla extract until smooth.
Step 4: Pour the wet ingredients into the dry ingredients. Stir with a spatula or wooden spoon just until the flour mixture is moistened and no streaks of dry flour remain. Be careful not to overmix.
Step 5: Pour the batter into the prepared loaf pan and spread evenly. Bake for 35-45 minutes, or until a wooden skewer inserted into the center comes out with moist crumbs attached (not wet batter).
Step 6: While the bread is still warm from the oven, prepare the topping. In a small bowl, combine the ⅓ cup granulated sugar, 1 tablespoon cocoa powder, and ¼ teaspoon ground nutmeg.
Step 7: Brush the top of the warm bread with the 3 tablespoons melted unsalted butter. Immediately sprinkle the sugar-cocoa-nutmeg mixture generously over the top of the bread, pressing gently to adhere. Let the bread cool completely in the pan on a wire rack.
Step 8: Once the bread is completely cool, prepare the milk chocolate ganache. Place the milk chocolate chips in a heatproof bowl.
Step 9: In a small saucepan, heat the heavy whipping cream over medium heat until it just begins to simmer around the edges (do not boil).
Step 10: Pour the hot cream over the chocolate chips. Let stand for 5 minutes without stirring, then gently whisk until the chocolate is completely melted and the ganache is smooth and glossy.
Step 11: Drizzle or pour the milk chocolate ganache over the cooled Chocolate Donut Bread. Allow the ganache to set slightly before slicing and serving. Enjoy!