Preheat the Oven: Position a rack in the center of the oven and preheat to 350°F. Bring the 2 quarts of water reserved for the initial water bath to a boil, then cover and keep it warm while preparing the batters.
Blend the Flan Base: Add the dulce de leche, evaporated milk, room-temperature cream cheese, vanilla extract, and kosher salt to a blender. Blend on medium-high speed for about 30 seconds, or until the mixture is completely smooth.
Add the Flan Eggs: Add the 5 room-temperature eggs to the blender and blend on medium-high for another 10–15 seconds, just until thoroughly incorporated.
Combine the Cake Dry Ingredients: In a large mixing bowl, whisk together the flour, granulated sugar, cocoa powder, baking soda, baking powder, cinnamon, and kosher salt until evenly distributed.
Prepare the Cake Batter: In another large bowl, whisk together the room-temperature buttermilk, coffee, melted and slightly cooled butter, egg, and vanilla extract. Gradually whisk in the dry ingredients until the batter is just combined. Avoid mixing beyond this point. Prepare the Bundt Pan: Generously coat a 10-cup Bundt pan with nonstick baking spray, making sure the pan is thoroughly covered.
Add the Chocolate Batter: Immediately scrape the chocolate cake batter into the prepared Bundt pan using a rubber spatula. Smooth the surface evenly with an offset spatula.
Layer the Flan: Slowly ladle the flan mixture over the chocolate cake batter. Pour carefully so the flan layer does not disturb the chocolate batter underneath.
Set Up the Water Bath: Place the filled Bundt pan in the center of a large roasting pan. Cover the Bundt pan tightly with aluminum foil. Carefully pour the boiled water into the roasting pan until it reaches approximately halfway up the sides of the Bundt pan.
Bake the Chocoflan: Bake at 350°F for 105–120 minutes, or until a skewer inserted into the center of the cake comes out clean.
Cool Completely: Carefully remove the Bundt pan from the water bath and remove the aluminum foil. Transfer the pan to a wire rack and allow the chocoflan to cool completely.
Chill the Cake: Once completely cool, cover the top of the Bundt pan tightly with plastic wrap. Refrigerate for at least 4 hours, preferably overnight, so the chilled layers can firm up before unmolding.
Prepare the Unmolding Water Bath: Place the chilled Bundt pan in the center of the roasting pan. Bring the 2 quarts of water reserved for serving to a boil, then immediately pour it into the roasting pan until the water reaches halfway up the sides of the Bundt pan.
Prepare the Kitchen Towel: Carefully dip the kitchen towel into the hot water. Wring it out over the sink or roasting pan, keeping it away from the Bundt pan, until the towel is damp but not dripping wet.
Steam the Chocoflan: Cover the Bundt pan and roasting pan with the damp kitchen towel. Let the setup stand for 15 minutes to warm the pan and help loosen the chilled cake.
Unmold the Chocoflan: Remove the towel and take the Bundt pan out of the water bath. Place a serving plate over the top of the Bundt pan, then carefully invert both together to release the chocoflan onto the plate.
Finish with Cocoa: Immediately dust the unmolded chocoflan with the 1 tablespoon natural unsweetened cocoa powder.
Serve and Store: Serve the chocoflan chilled or at room temperature. Keep leftovers tightly covered with plastic wrap or place slices in an airtight container and refrigerate for up to 3 days.
