Bring the water
to the boil, remove from the heat and stir in the
sugar. Heat gently, stirring, until the sugar has
dissolved. Then boil rapidly until the mixture
becomes syrupy, or reaches the "thread" stage. To
test, place a little syrup on the back of a dry
teaspoon. Press a second teaspoon on to the syrup
and gently pull apart. The syrup should form a fine
thread. If not, return to the heat, boil rapidly and
re-test a minute later.
Whisk the egg
yolks together in a bowl. Continue to whisk
while slowly adding the sugar syrup. Whisk until
thick, pale and cool.
Beat the butter
until light and fluffy. Add the egg mixture
gradually, beating well after each addition, until
thick and fluffy. For Chocolate or Coffee Creme au
Beurre, fold in the flavoring at the end. If you
prefer a citrus flavor, follow the instructions
above.