Place salmon fillet in pan and just cover with cold water. Bring to a boil, then reduce heat and simmer for 5 minutes.
Remove from pan and cool completely on a plate, about 30 minutes.
Place salmon in food processor and pulse briefly.
Add cream cheese, butter and lemon juice; puree until smooth. Season with salt and pepper.
Transfer to a bowl, cover and chill for 30 minutes. (Can be made to this point the day before.)
Spoon pt into piping bag with star nozzle and pipe onto vegetables or crackers; sprinkle with chopped chives. Or spoon it into a serving bowl and serve with crudits.