• 1 cup white sugar
• 14 ounce can sweetened condensed milk
• 14 ounces whole milk
• 3 eggs
• 1 teaspoon vanilla extract
• 3 tablespoons rum

Preheat oven to 350 degrees. Prepare a bain marie, or water bath, by filling a 9 inch heatproof container with water. Melt sugar in a nonstick pan over medium low heat, stirring constantly until melted, 7 to 10 minutes; be careful to keep it from burning. Pour sugar into a flan mold or round cookie tin, coating the sides to ensure that the egg and milk mixture in the next step will not touch the container. Pour sweetened condensed milk into a bowl. Fill the empty can with whole milk and add to the bowl; stir in eggs, vanilla extract and rum. Blend well. Fold mixture with a spatula or tap against the counter to remove air bubbles. Pour milk mixture into the slightly cooled flan mold. Put the lid on and place inside the water bath; don't let the water go over the rim. Bake the quesillo in the bain marie in the preheated oven for 45 minutes. Pry lid open with a knife carefully; continue baking until set, about 15 minutes more. Let quesillo cool to room temperature, at least 25 minutes; refrigerate 8 hours to overnight. Slide a knife around the edges of the mold to loosen and invert onto a plate.