In a sauce pan combine water, butter, salt and sugar. Bring to a boil. As soon as mixture boils, remove from heat and add, all at once, the flour. Briskly beat with a wooden spoon until smooth. Return to the heat as necessary.
Remove from heat and transfer to a mixing bowl. Beat 1 egg into flour mixture until smooth. Repeat with second egg. Transfer to a pastry bag fitted with a 1/2" tip.
On a parchment paper–covered baking sheet, pipe 2" diameter mounds, about 3" apart. Brush gently with the beaten egg white.
Bake for about 30 minutes until brown. Transfer to a rack to cool. When cool, slice horizontally about one–third down from the top.
Beat cream with an electric mixer until soft peaks form. Add sugar and continue beating until stiff. Melt chocolate over barely simmering water until melted and add to whipped cream. Beat until well mixed.
Put cream in a pastry bag fitted with a 1/2" tip. Pipe the cream into the bottoms of the cooled puffs and replace tops. Serve immediately.