In a medium saucepan, combine granulated sugar with a splash of water over medium heat. Stir gently until the sugar dissolves, then let it cook undisturbed for about 8–10 minutes until it turns a beautiful golden color. Pour the caramel into a round baking pan and allow it to cool and harden.

In a mixing bowl, whisk together large eggs, sweetened condensed milk, whole milk, and vanilla extract until combined. Be careful not to overbeat; the mixture should be smooth and slightly frothy.

Pour the prepared custard mixture over the hardened caramel in the baking pan. Cover the pan with aluminum foil and place it inside a larger baking dish filled with warm water halfway up the sides of the flan pan.

Preheat your oven to 350°F (175°C) and bake the Spanish Flan for approximately 1 hour to 1 hour 15 minutes, or until set.

Once baked, carefully remove the flan from the oven and let it cool at room temperature for about 30 minutes. After, transfer it to the refrigerator and chill for at least 4 hours.

To serve, run a knife around the edges to loosen the flan, then invert it onto a serving platter to enjoy.