Clean the spinach and remove roots and discard the yellow leaves. Wash 4-5 times in cold water. While washing the spinach, tear the big and long leaves in half with your hands.
Place the spinach in a big metal or glass bowl. Boil 4 cups (1 litre) water and pour over the spinach. Stir gently with a wooden spoon and drain in a colander. Rinse the spinach with cold water 2-3 times. Squeeze out all the water with your hands.
Spread the spinach in a mixing bowl and season with soya sauce, garlic, red chilli powder, sesame seeds, salt and black pepper and mix well. Slice the white part of the green onions thinly at a slant and add sesame oil. Mix one more time and serve.