Fill a small pan with salted water and place it over high heat. Once boiling, add the green beans.
Turn the heat lower and cook the beans for a couple of minutes until they are nearly tender, kind of al dente. Don’t overcook the beans. Immediately drain the cooked beans and refresh them under cold running tap water. This will stop the cooking process and will keep the beans bright green.
Place the beans in the fridge to chill for 15 minutes. Then chop the beans up into small bits. Add them to a mixing bowl together with the chopped onion. Season with a pinch of pepper, salt and garlic powder.
Stir the beans well. Drizzle with the olive oil, the toasted sesame oil and the balsamic vinegar.
Stir the beans again. Check the seasoning. Add extra pepper or salt to taste. Put the salad in the fridge for 15 more minutes. Then divide the herring fillets over plates and add the the chilled bean salad. Serve immediately.