Place liquid, butter, salt and sugar, if using, in a medium saucepan and bring slowly to a simmer. Turn off heat and add the flour all at once. Stir vigorously with a wooden spoon until it forms a ball. Return to medium heat to dry the paste so it will have the maximum puffing ability: turn the ball around in the pan, pressing it against the sides and flipping it over, until butter starts oozing out and the paste no longer sticks to your fingers. Remove from heat and let cool a bit. Turn the paste into a medium bowl or the bowl of an electric mixer fitted with a paddle and beat in the eggs, one at a time, with a wooden spoon or the paddle. Each time you add an egg, the mixture will become slippery and messy but will then come together, at which point you can add the next egg. Load mixture into pastry bag with a round tip (1/2 or 1-inch depending on size puff desired) and pipe out as required. It will give the fullest puff if used right away but can be held for several hours. Basic proportions for Pate a Choux are 1:1:1:1/2, or 1 cup liquid, 1 cup flour:1 cup egg:1/2 cup butter. Water makes choux more crisp, milk makes them more tender, Puffs expand when cooked as water in batter turns to steam and explodes the dough. Pate a choux is an extremely versatile pastry that can be the base of many sweet and savory dishes. It can take many forms: be poached as gnocchi, baked to form hollow puffy balls that can be filled with various things, or fried as fritters and sprinkled with sugar. It is neutral in flavor so is adaptable to any cuisine. 10/23/96 SHOW