Preheat the oven to 355°F. Set two 5-inch round cake pans, ramekins, or custard cups next to the stovetop.

Combine 3 tablespoons sugar and 1 tablespoon water in a heavy saucepan. Cook over low heat until melted and golden, about 10 minutes, brushing down sides of the pan with a pastry brush and swirling the pan occasionally. Do not stir.

When ready, pour the caramel into the cake pans, tilting to coat the bottoms. Use oven mitts. Try to work quickly because the caramel will start to harden in a matter of seconds. Let stand for 15 minutes to set.

In a heavy-bottom medium saucepan, combine condensed milk and vanilla seeds. Bring to a simmer over medium heat. Remove from heat, add chocolate chips, and mix well to combine. Set aside for 30 minutes. When cool, beat in the egg and egg yolk, mixing until thoroughly combined.

Pour the mixture over the caramelized sugar in the cake pans. Place the cake pans in a larger baking pan and pour boiling water into the larger pan to a depth of around 1 inch. Place in the preheated oven and bake until the center is just set, about 40 minutes.

Transfer the two cake pans with flan to a wire rack and let cool for 1 hour, then refrigerate overnight. To unmold, run a knife around edges and invert onto a rimmed serving plate.

Decorate with a bit of powdered sugar, fresh mint leaves, and red berries just before serving.