Score skinless side of fish with shallow diagonal cuts; score again at a 90 degree angle to the first cuts. Cut fillet into 3 inch squares.
Combine marinade ingredients in a bowl and add fish; turn to coat. Let stand for 10 minutes.
Combine sauce ingredients in a bowl; set aside.
Dip fish squares in egg, drain briefly, then coat with flour. Shake to remove excess.
Heat oil in a wok to 375 degrees F. Deep-fry fish, turning once, until golden brown, 2 to 3 minutes. Remove and drain on paper towels. Keep warm.
Place another wok over medium-high heat until hot. Add 1 tablespoon oil, swirling to coat sides. Add onion; cook, stirring, until softened, about 10 seconds. Add pineapple and sauce and cook, stirring, until sauce thickens, about 1 minute.
To serve, arrange fish on a serving plate. Pour sauce over fish and sprinkle with pine nuts.