Preheat the oven to 355°F (180°C).

Place the granulated sugar in a heavy-bottomed saucepan. Cook over medium heat, stirring frequently, until the sugar dissolves and turns into caramel. This will take about ten minutes. Be vigilant as caramel can burn quickly.

Once the sugar has caramelized, pour it into a round ceramic flan pan that has been coated with nonstick cooking spray.

Combine eggs, vanilla extract, cinnamon, nutmeg, and mashed sweet potato in a mixing bowl, then add evaporated and sweetened condensed milk, blending the mixture in a blender for a smoother and well-integrated flan mixture.

Pour the custard mixture over the caramel in the flan pan until it reaches a depth of about one inch.

Place the flan pan in a larger baking dish and add hot water to the larger dish until it reaches about one inch up the sides of the flan pan.

Bake in the preheated oven for about 35 to 40 minutes, or until a knife inserted into the center of the custard comes out clean.

Remove the flan pan from the water bath and allow it to cool to room temperature.

Refrigerate the flan for at least four hours, or until it is fully set.

To serve, run a knife around the edge of the custard to loosen it from the pan. Invert the pan onto a serving plate, allowing the caramel to drizzle over the flan.