Mushroom, Ginger-Soy Fried Flounder

1-1/4 lbs. flounder fillets, cut into 1x2 inch squares, patted dry
1/3 cup cornstarch
2 egg whites
1/8 tsp black pepper
2 tbsp plus 2 tsp. peanut oil
1-1/4 tsp ground ginger or 1-1/4 tsp. fresh, peeled and finely minced
2/3 cup mushrooms, thinly sliced
2/3 cup scallions, chopped
1 tbsp plus 1 tsp. tamari soy sauce

Combine fish squares and cornstarch in a bowl. Toss to coat. Beat egg whites and black pepper until foamy. Dip coated fish pieces into egg white mixture.
Heat oil in a heavy nonstick skillet or wok over medium high heat. When oil is very hot, fry coated fish 3-4 minutes, a few at a time, until golden. Remove with a slotted spoon, drain on paper towels and keep warm.
Discard all but 1-1/4 tsp. oil. Stir-fry ginger, mushrooms and scallions 1-2 minutes in same wok or skillet. Stir in soy sauce. Serve fish with sauce.