Mushroom Barley Soup

[adapted from the Hip Chick's guide to Macrobiotics by Jessica Porter, p.227]
[barley is not gluten free]

8 button mushrooms, sliced
1/2 cup barley, best soaked in spring water overnight
6 cups filtered or spring water
1 inch piece kombu [seaweed, buy at Whole Foods]
3 thin slices ginger
2 medium onions, diced
3 tablespoons rolled oats or brown rice flour
21/2 tablespoons barley miso or to taste
1 teaspoon lemon juice (optional)
fresh watercress or parsley for garnish

Place mushrooms, barley, water, kombu, and ginger in a pot. Bring to a boil and simmer 40 minutes or until barley is softened. With a handheld food processor, whiz the rolled oats into almost a flour.
Heat bit of water in a skillet over medium heat and saute the onions. Add the flour and saute  with onions, coating them well. Take 1/2 cup of soup from the pot and slowly stir it into onion-flour mixture, avoiding lumping. Add to soup mixture.
Dilute miso in a cup with some of the soup. Add this liquid to the soup and let simmer 5 minutes. Right at the end, squeeze the lemon juice, if desired, into the soup. Garnish and serve.
Variation: Feel free to build on this soup with corn kernels, diced celery, and roasted red pepper toward the end.