In a sauce pan combine water, butter, and salt. 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.
On a parchment paper–covered baking sheet, using two teaspoons, place walnut-size mounds about 3 inches apart.
Bake for about 30 minutes until brown. Cool slightly before filling.
Make a quarter inch round hole in the base of each puff with a sharp knife — insert the knife tip and rotate the tip to make a round hole. Using a pastry tube fitted with a quarter inch tip, fill each puff with foie gras mousse.