Cook sugar in a sauce pan over a moderate heat. Watch the sugar closely as it heats. As the sugar begins to melt and turn from a clear liquid to a golden brown color around the edges, use a spatula move the liquefied sugar from the edges of the saucepan to the center. Be careful not to over stir the caramel- the sugar may start to clump up before it has a chance to melt. Caramel is done when it is just past the smoking point, and it has a deep amber color. At this point, turn off the heat and add the espresso if you like the taste of it.

Immediately pour the caramel into a baking pan and tilt the pan to make sure that the caramel is coated evenly at the bottom of the baking pan.

Preheat oven at 350 degree. Make a water bath for flan by placing a baking tray in the middle rack of the oven and add hot water to ⅔ of the tray.

Whisk eggs until blended. In a separate mixing bowl, stir boiling hot water and condensed milk until dissolved. Add whole milk and mix well. Pour the mixture into the eggs bowl and do a quick whisk. Add 1 bag of vanilla or vanilla extract. Strain it.

Pour flan mixture in a baking pan, place baking pan in the hot water bath. Place a piece of foil loosely on top of the baking pan to prevent flan from burning.

Bake for about 45 minutes to 50 minutes depend on the type and size of your baking pan. The flan is ready to be removed from the oven when the edges are set. Gently shake the baking pan, the center of the custard should jiggle slightly. You can also insert the tip of a toothpick into the custard near the center. If the flan is still liquid, it needs more time in the oven. Remove from the water bath and let them cool down.

Transfer flan to the fridge and chill it for a few hours. Refrigerating the flan overnight is best. When it's ready to serve, loosen it from the pan with a knife and transfer onto a dessert plate and top with your choice of fruits or just eat it plain.