For the homemade caramel sauce, add the sugar and water to a small saucepan and stir to combine. Place the pot over medium heat, and cook until the sugar dissolves, or until no granules remain, turns clear, and bubbles, about 3-4 minutes.
Let the mixture cook and do not stir it. Allow it to bubble and swirl the saucepan occasionally. Using a pastry brush, brush the sides of the pan occasionally to prevent crystallization.
Continue cooking and occasionally swirling the mixture until it turns a deep amber color and thickens, about 10-12 minutes.
Next, add in the butter, whisking slowly until melted and combined. Stir constantly. Add in the vanilla and salt, and mix to combine. Set aside to cool completely, about 1 hour.
Preheat the oven to 350°F.
Liberally grease a full-sized, 12-cup Bundt pan with cooking spray. Pour the caramel sauce in the bottom of the Bundt pan evenly. Set aside.
In the bowl of a stand mixer, whisk together the flour, cocoa powder, baking soda, and salt until blended.
Meanwhile, in a glass bowl, heat the chocolate and butter together in a microwave on high power for 30 seconds. Stir, then heat again for another 30 seconds or until melted and smooth.
Whisk the sugar into the melted chocolate mixture, and pour the melted chocolate mixture into the stand mixer bowl with the dry ingredients.
Beat slowly, then stream in the whole milk.
Beat until combined, followed by adding the eggs one at a time, as well as the vanilla extract and vanilla paste.
Pour the chocolate cake batter into the prepared pan in an even layer.
In a large blender, add the flan ingredients and process for 1 minute or until thin and combined.
Hold a rubber spatula over the bundt pan. Pour the flan mixture directly over the rubber spatula so that it evenly distributes above the cake batter without indenting it. This “buffering” technique will ensure that the flan mixture sits on the cake batter in an even layer.
Carefully transfer the Bundt pan to a larger roasting pan and nestle it inside.
Pour hot water into the roasting pan until it hits about halfway up the Bundt pan. Cover the pan with aluminum foil.
Bake for about 90-105 minutes. To ensure doneness, measure the flan’s internal temperature by inserting a thermometer about 1 ⁄ 2 way through the bundt pan to reach the flan. The flan is done when the temperature reads 175ºF.
Remove the roasting pan from the oven, and remove the bundt pan from the water bath.
Cool completely to room temperature, about 1 hour, then refrigerate for at least 8 hours, preferably overnight. This step is mandatory to ensure that the flan properly sets.
Just before serving, place the bundt pan back into the roasting pan and add about 1-2 inches of hot tap water.
Let sit in the water for about 5 minutes.
Take a platter or cake stand and flip it upside down on top of the Bundt pan. Throughout the baking process, the two layers will naturally invert so that when the cake is flipped onto a serving dish, the flan rests on top and the chocolate cake on the bottom.
Working quickly and carefully, invert the bundt pan onto the serving dish and let set for a second so all the caramel drips onto the flan cake. Remove the bundt pan from the top of the cake slowly and carefully.
Serve while cold and store leftovers covered in the fridge. Spoon any extra caramel in the Bundt pan over the top of the flan.
Note: This recipe was originally created for Rodelle by Hayley from The Domestic Rebel. This recipe was updated in 2024 with support from ADM Intern, Katie Scheid
