In a large bowl, add the eggs, milk, sugar, and vanilla extract (if using). Whisk everything together well until fully combined. Caramelize the flan molds and fill them with the flan mixture.

Fill a skillet or pot halfway with water and heat over medium. When the water is hot, place the molds with the flan mixture into the skillet. Cook over medium heat for about 20 minutes. After that, cover the flans with a paper towel and then with a lid. Continue cooking over medium heat for another 15 minutes.

Check if the flan is set by inserting a toothpick. If needed, cover again and cook for a few more minutes until fully set. Let cool to room temperature, then refrigerate for a few hours. Enjoy these delicious homemade egg flans!