Add 2 cups coconut milk to a small saucepan, along with sugars, salt, vanilla extract and coffee syrup
. Cook over medium heat. Stir well to dissolve sugar. When mixture begins to steam, slowly pour 1 cup warm liquid into yolks, while continuously whisking. Transfer egg mixture into saucepan. Stir occasionally, cooking over medium heat until mixture coats the back of a wooden spoon or rubber spatula.