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Preheat the oven to 400° and position 2 racks in the upper and lower third. Lightly grease 2 large rimmed baking sheets.
In a saucepan, bring the water, butter and salt to a boil. Off the heat, add the flour and stir vigorously until combined. Return to the heat and cook over moderate heat, stirring, for 1 minute. Scrape the mixture into a bowl and, using an electric mixer, beat at medium speed for 1 minute. Add the eggs, 1 at a time, beating well after each addition, until thick, smooth and shiny.
Transfer the dough to a pastry bag fitted with a 1/2-inch plain tip. Pipe 1-inch mounds onto the prepared baking sheets, about 3/4 inch apart. Using lightly moistened fingertips, smooth the tops. Sprinkle with the poppy seeds and bake for 20 minutes, shifting the pans halfway through, until the puffs are risen and golden. Lower the oven to 250°.
With the tip of a knife, poke a hole into the side of each puff and return to the baking sheet. Bake for 10 minutes longer, with the oven door slightly ajar, to dry out the centers. Transfer to a rack and cool.
In a food processor, combine the smoked salmon with the cream cheese, sour cream, mustard and garlic and process until smooth; season with Tabasco. Transfer the filling to a pastry bag fitted with a 1/4-inch tip. Pipe the filling into the holes in the sides of the puffs and transfer to a serving plate. Serve right away.
The unfilled baked puffs can be frozen for up to 1 month; recrisp in a 325° oven. The filling can be refrigerated for up to 3 days.