In a small saucepan, combine butter, water, sugar, and salt. Bring to a rapid
Remove from heat and add flour (all at once), stirring vigorously.
Return to low heat and cook, beating briskly, until dough pulls away from sides
of pan and forms a ball.
Remove from heat and add eggs one at a time, beating
well after each addition.
Beat by hand or with electric mixer on medium until
smooth, glossy, and elastic. Stir in vanilla.