Preparation Steps

• Heat the oven to 350°F. Grease a 10 to 12-cup Bundt pan thoroughly, then dust the interior with a little cocoa powder, tapping out the excess.
• Bloom the cocoa: In a heatproof bowl, whisk the hot brewed coffee into the sifted dark cocoa powder until silky and no lumps remain. Set aside to cool until warm, about 5 minutes.
• In a medium bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon.
• In a large bowl, vigorously whisk the sugar, eggs, and vanilla until slightly thickened and pale, 1½ to 2 minutes. Slowly stream in the oil while whisking until the mixture looks glossy and cohesive.
• Whisk in the sour cream and milk until smooth, then whisk in the warm cocoa–coffee mixture until evenly combined.
• Switch to a spatula and fold the dry ingredients into the batter in two additions just until no dry streaks remain. Let the batter rest 5 minutes to hydrate the cocoa and settle bubbles.
• Scrape the batter into the prepared pan and tap the pan firmly on the counter 2–3 times to release air pockets.
• Bake until the top springs back and a toothpick inserted near the center comes out with a few moist crumbs, 40 to 46 minutes. Rotate the pan once if your oven has hot spots.
• Cool on a rack for 12 minutes, then loosen the edges with a thin knife and invert onto the rack. Cool completely before glazing.
• Make the drizzle: Microwave the cream cheese in a bowl for 10–15 seconds until just pliable. Whisk in the powdered sugar, cocoa, and vanilla. Thin with milk or cream, 1 teaspoon at a time, to a thick-but-pourable consistency. Whisk in the light corn syrup if using for extra sheen.
• Spoon or pour the glaze over the cooled cake in slow zigzags, letting it cascade down the sides. Allow 15 minutes for the glaze to set before slicing.