Adjust oven rack to middle position and heat oven to 350 degrees.
Grease 12-cup nonstick Bundt pan. Cook sugar in a pan over meadium heat until a nice amber color. Pour into pan to coat bottom.
Combine flour, cocoa, baking soda, and salt in bowl; set aside.
Combine chocolate and Extra Virgin Olive Oil from Spain in large bowl and microwave at 50 percent power, stirring occasionally, until melted, 2 to 4 minutes.
Whisk buttermilk, sugar, eggs, and vanilla into chocolate mixture until incorporated. Stir in flour mixture until just combined.
Pour batter over caramel in prepared pan.
For the flan:
Process all ingredients in blender until smooth, about 1 minute. Gently pour flan over cake batter in Bundt pan and place pan in large roasting pan. Place roasting pan on oven rack and pour warm water into roasting pan until it reaches halfway up side of Bundt pan.
Bake until toothpick inserted in cake comes out clean and flan registers 180 degrees, 75 to 90 minutes.
Transfer Bundt pan to wire rack. Let cool to room temperature, about 2 hours, then refrigerate until set, at least 8 hours. (Remove roasting pan from oven once water has cooled.)
Place bottom third of Bundt pan in bowl of hot tap water for 1 minute.
Invert completely flat cake platter, place platter over top of Bundt pan, and gently turn platter and pan upside down. Slowly remove pan, allowing caramel to drizzle over top of cake. Serve.
As presented at the 2017 Olive Oil Conference, Chicago (Ilinois)