Sweet and Sour Fish

I finally was able to use the thin green onions growing on my kitchen table. I like the sauce of this recipe. It's light and not too tangy as the usual sweet and sour sauce I've had before. This recipe is from "The Quick and Easy Japanese Cookbook" by Katsuyo Kobayashi, an "Iron Chef" winner.

5-6 dried shiitake mushrooms
1 boiled bamboo shoot, 7 oz/200g (optional for me as I didn't have this in my pantry)
1/2 carrot
1/2 onion
1 knob (1 inch/2-1/2 cm) fresh ginger (I used grated ginger)
4-5 thin green onions or chives
4 fillets of flounder, or cod, or any other white fish (each 5 oz/140g)
Potato starch for dusting fish + 1 tbsp potato starch dissolved in 1 tbsp water (I used flour)
vegetable oil for deep frying (I don't like deep frying so I just sauteed the fish)

Sauce:
1/2 cup water
1 tbsp ketchup
1 tbsp rice vinegar
1 tbsp sugar
1 tbsp sake (I didn't have sake so I used rice wine)
1 tbsp light-colored (usukuchi) soy sauce or 2 tsp regular soy sauce + 1 tsp salt
1/2 tsp sesame oil

1. Reconstitute shiitake mushrooms by soaking them in warm water for 10 minutes until they soften. Drain. Discard stems and cut caps into thin strips. Cut the bamboo shoot and the carrot into thin slices and then into matchsticks. Slice the onion finely. Cut the ginger into thin strips. Cut green onions into 1-inch lengths.

2. Cut the fish into bites-sized pieces and dust with potato starch. In a wok or fry pan, heat the oil to medium, add the fish, and deep-fry until cooked through and crispy. Remove from heat and arrange fish on a dish.

3. In a small pan, combine sauce ingredients, except sesame oil. Add all the vegetables and bring to boil until carrot softens. Stir in the dissolved potato starch and remove from heat as soon as the mixture thickens and glazes.

4. Add green onions and sesame oil, and mix quickly. Pour the sauce over the fish and serve immediately.