1. Prepare the Crust:

1. Preheat oven to 350°F (175°C).
2. In a small saucepan, combine sugar and water. Cook over medium heat, stirring constantly, until sugar dissolves and turns into a golden caramel. Pour caramel into a 9-inch round baking dish, tilting to coat the bottom evenly.
3. In a blender, combine eggs, condensed milk, evaporated milk, vanilla extract, and cocoa powder. Blend until smooth.
4. Pour the mixture over the caramel in the baking dish. Sprinkle chopped Ferrero Rocher chocolates on top.
5. Place the baking dish in a larger roasting pan. Fill the roasting pan with hot water until it reaches halfway up the sides of the baking dish (water bath).
6. Bake for 45-50 minutes, or until the flan is set but still slightly jiggly in the center.
7. Remove from oven and let cool to room temperature. Refrigerate for at least 4 hours or overnight.
8. To serve, run a knife around the edges of the flan and invert onto a serving plate. Garnish with whipped cream if desired.