Put an oven rack in the middle of the oven and preheat to 350 degrees F. Grease a Bundt pan with butter.
First prepare the cake batter. Add the butter and sugar to a bowl and, using an electric hand mixer or a stand mixer, beat until light and fluffy. Then beat in 1 egg.
Sift together the flour, baking soda, baking powder and salt in a medium bowl. Mix the buttermilk, cocoa powder, tequila, triple sec and vanilla extract in a medium bowl. Beat half of the flour mixture half of the buttermilk into the egg mixture. Repeat, ending with the flour mixture. Blend until well incorporated.
Now prepare the flan mixture. In a blender, combine the condensed milk, evaporated milk, cream cheese, the remaining 3 eggs and vanilla extract. Blend on high for 30 seconds.
Scoop the cake batter into the prepared Bundt pan. Then slowly pour the flan mixture over the cake batter. Add about 1-inch of hot water to the roasting pan.
Carefully slide the pan into the oven and bake until the surface of the cake is firm to the touch, or an inserted toothpick comes out clean, about 1 hour. When the cake is done, remove from the water bath and cool completely to room temperature, about 1 hour.
Run the tip of a sharp paring knife along the edge of the Bundt pan to loosen. Invert a large, rimmed serving platter over the Bundt pan, grasp tightly together, jiggle it a little and flip over to release the chocoflan from the pan. Garnish the cake with some chopped pecans. Place some mixed berries in the center of the chocoflan then sprinkle the entire thing with powdered sugar and serve.