Combine mousse ingredients in bowl of food processor and blend until smooth. Chill at least 30 minutes. No more than an hour before serving, soften mousse with wooden spoon and put in pastry bag. Pipe mousse into puffs. (May also be piped onto cucumber rounds.)
Heat 3 tbl butter in small skillet and saute onions until transluscent. Season w/salt & pepper. Melt remaining butter in separate saucepan over med. heat.
Add flour and cook 3-4 minutes, stirring constantly. Add curry powder and cream. Cook stirring constantly, until smooth, about 5 minutes.
Add onion mixture. If sauce is too thick, add a little more cream. Check seasoning. Spoon warm filling into puffs and serve immediately.
Combine all filling ingredients in mixing bowl. Spoon into puffs.