I am known for my flan. I grew up eating flan—like we all do in Puerto Rico. I am not a big fan of flan that has like 20 eggs in it where all you taste is the egg So my flans have only six or eight eggs.
Calabaza is a West Indian gourd, much like pumpkin. Roasting the calabaza enhances the flavor because the sweetness is brought out with the slight caramelization. What you see oozing out of roasted calabaza is actually a little sugar.
Preheat the oven to 400°F. Place the sugar in an 8-inch-diameter flan mold and bake until the sugar caramelizes (liquefies and turns a brown color), about 15 minutes. Set aside and let cool completely.
Cut the calabaza into large-ish pieces and remove all the seeds.
Place skin side down on a rimmed baking sheet. Cover the entire baking sheet with foil. Roast until the pumpkin is soft and a knife is inserted easily, about 20 minutes. Uncover and set aside to cool. Reduce the oven temperature to 350°F.
With a spoon, scoop the pumpkin pulp from the skin. Measure out 1 cup and place in a food processor. Puree until the pumpkin is almost liquid. Add the condensed milk, evaporated milk, eggs, and vanilla and puree until the mixture is smooth.
Pour the egg mixture into the mold to cover the caramel, cover with foil, and place in the center of a large roasting pan. Transfer the pan to the oven and pour water in the pan to come halfway up the sides of the mold. Bake until a knife inserted in the center of the flan comes out clean, for 1 1/2 to 2 hours,. Allow the flan to cool completely.
To serve, cut around the edges and invert onto a serving plate. Cut into 6 to 8 pieces. Place a slice on each plate and drizzle with the caramel sauce from the mold.