In a small, heavy saucepan combine the 1/2 cup sugar and the water. Cook over medium-high heat until the sugar dissolves, then keep cooking about 5 more minutes, until a nice golden brown. Immediately pour into 6 (6 oz.) custard cups, tilting so that the caramelized sugar coats the bottoms.
Whisk together the remaining sugar, the eggs, salt and egg yolks.
Heat milk over medium-high heat to 180 (tiny bubbles will form around the edge); don't let it boil. Gradually add hot milk to egg mixture, stirring with a whisk. Stir in liqueur. Strain through a sieve into a bowl, discarding solids. Divide evenly into the custard cups.
Place cups in the bottom of a broiler pan; add hot water to a depth of 1 inch. Bake at 325 for 40 minutes or until centers barely move when cups are touched. Remove cups from the pan and cool completely on a wire rack. Cover and chill at least 8 hours.
To serve, loosen the edges of each flan with a knife. Cover each cup with a dessert plate (upside down), and invert flans onto plates.