1. Remove skin from fish; break into pieces.
2. Pulse onion in a food processor until finely chopped. Add cream cheese; pulse 3 times or until blended. Add fish, lemon juice, and next 2 ingredients; pulse 3 times or until thoroughly mixed, stopping to scrape down sides. Serve with crostini.
*Substitute smoked tuna or trout for the bluefish, if desired.