Before you start with your cooking, prepare a water bath (Bain Marie) by placing the ramekins into a bottom flat baking shape together with some warm water. See picture as a reference.
Add to a mixing bowl the condensed milk, 2 whole eggs and 2 egg yolks and mix well.
Now prepare the Caramel by placing half amount of the powdered sugar into the pot with the 2 Tablespoons of Water. Keep it on a very low flame, it has to heat up gradually and make sure there are not lumps. Slowly you will notice that the sugar is melting and at that point you add the remaining sugar. Take care that you don't burn your caramel. Believe me it happens very quickly, so when you see the sugar melted and slowly turning into a yellow golden, stir well. A few seconds later it will be turning brown and at that point you can take it away from the heat.
Don't waste time and directly pour the caramel into the ramekins, no delays or it will get hard in less then a few seconds! (After emptying the pot with the caramel, pour hot water into it. Best way to wash the pot easily)
Preheat your oven to 350 Fahrenheit/ 180 Celsius!
In a pot add the milk, cut lengthwise into your vanilla bean and collect the small black seeds with a spoon. Add the seeds and empty vanilla bean into the milk and heat up for a short time. The vanilla flavor will incorporate into the milk while it's simmering. Once it is hot enough, remove from the heat and let the vanilla bean steep in the milk for a few minutes. Never boil and don't allow the milk to grow a skin on top or the vanilla seeds might get stuck in the skin. Discard the empty vanilla bean.
Pour the vanilla milk into the egg condensed milk mixture and whisk heavily so that all ingredients are well incorporated. You should do that quickly because you don't want any egg lumps to form with the hot milk.
Then pour the mixture over the caramel into the ramekins and place the baking shape with the water bath and ramekins into the oven and bake at 350° Fahrenheit/ 180° Celsius for about 18 minutes or until the top has turned golden brown. You can check too if it's cooked in the center by poking with a knife, if the knife comes back clean it is ready, otherwise the flan might take a few more minutes in the oven to bake properly.
Serve in the Ramekin or turn over into a plate. I prefer the flan cold, so you can keep them in the fridge to cool before serving or serve them still warm (but cooled down).
Notes
A ramekin is a small ceramic dish to serve individual food.