Bring the water, butter and vanilla to a boil. Add flour.
Stir constantly until it leaves the side of the pot and forms a ball. Remove and cool.
Beat in the 4 eggs, one at a time until smooth.
Drop by T. onto parchment lined cookie sheets (You want 8 for nice large ones) and bake at 400 degrees for about 40 minutes.
(Pro tip: Can poke with a toothpick once out of the oven, then return them to the oven with it shut OFF and crack the door while they cool. This prevents them from deflating)
LET COOL.
Slice in half and pipe or scoop in Mom's filling. Dust with powdered sugar or pour on melted chocolate.
