In a saucepan over medium heat, bring water and butter to a boil. Add flour and salt all at once. Stir until smooyh ball forms. Remove from heat and let stand 5 minutes. Add eggs, one at a time, beating well after each. Beat until smooth.
Cover a baking sheet with foil; grease foil. Drop batter into six mounds onto foil. Bake at 400° for 15 minutes.
Reduce heat to 350°; bake 30 minutes longer. Remove puffs to a wire rack. Immediately cut a slit in each for steam to escape.
In a mixing bowl, beat cream until soft peaks form. Gradually add sugar and cocoa, beating until almost stiff.
Split puffs and remove soft dough. Add filling; replace tops. Melt chocolate and butter; stir in sugar and water. Drizzle over puffs. Chill. Yield: 6 servings.