Bring chicken (or vegetable) stock to a simmer in a medium saucepan.

Add scallions (6 tablespoons), spinach (or arugula), mushrooms, soy sauce, and white pepper to the simmering stock.

Cook for 3 minutes at a low simmer.

While stirring the stock with a fork, gradually add the beaten eggs in a slow, steady stream.

Continue stirring to create egg shreds or ribbons.

Cook until the eggs are set (about 1 minute).

Remove the saucepan from the heat.

Ladle the soup into bowls.

Garnish with remaining scallions.

Season with salt to taste and serve immediately.