Place the butter
and water in a medium-sized saucepan
, and heat gently, stirring occasionally, until the butter melts, then bring the mixture to a rolling boil
the flour and salt into a large bowl. Make a well in the middle of the flour, and add the egg. Pour the hot liquid into the flour and stir with a wooden spoon to mix.
Spread the mixture out on a large plate with the wooden spoon and cool, about 15 minutes. Then wrap in plastic wrap
, and place in the refrigerator for 30 minutes, or until firm. Use according to the recipe you are making.