Carefully pour the batter to the prepared cake pan, then smooth it out. Gently pour in the flan using a sieve or ladle to avoid disrupting the cake batter.
Place the square of aluminum foil greased side down onto the Bundt pan and wrap it around the outside edge of the pan. No need to wrap it super tightly, but try not to just leave it sitting on top. Place the Bundt pan in a large roasting pan. Transfer the roasting pan to a pulled-out oven rack. Fill the roasting pan roughly two-thirds of the way up the sides with warm water (a large pitcher with a good spout is your best friend here) and close the oven door.
Bake until a short bamboo skewer or cake tester comes out with only a few crumbs from the cake, 1 hour 45 minutes to 2 hours. Start checking on it at the 1 hour 45-minute mark and note that if the skewer goes into the flan its tip might be a little wet because the flan won’t have set yet; it will do that in the refrigerator.
Carefully remove the roasting pan from the oven and carefully lift the Bundt pan out of the water bath and place it on a cooling rack. Let the chocoflan cool completely at room temperature with the foil tented on top of the pan; this will take about 2 hours.
Place the foil tightly back onto the pan and place the chocoflan in the refrigerator to set completely. This should take 4 to 5 hours, but an overnight 6- to 8-hour chill is ideal for the flan to set up perfectly.
When you’re ready to serve, carefully use the tips of your fingers to pull the cake away from the edge of the pan then place a large serving platter or cake stand over the Bundt pan and flip over to invert. Depending on your pan the chocoflan might be a little difficult to invert at first. If this is the case dip the bottom of the pan into a bowl of warm water for 5 to 6 minutes and try to invert the cake again.
Once you are ready to serve, serve each slice with a drizzle of dulce de leche, caramel sauce, or cajeta, and finish with a sprinkle of chopped pecans.
To store, carefully wrap it in plastic wrap and keep in the refrigerator for up to 3 days.