In a small sauce pot, bring 3 cups of water to a gentle boil. Add the pre-soaked adzuki beans, reduce heat to low, cover, and simmer for 30 minutes, while you prepare the soup.

Soak the porcini mushrooms in 1 cup of very hot water, while you prepare the soup.

Heat 1 tablespoon of vegetable stock in a medium (3 to 4 quart) dutch oven or stock pot over medium until until it begins to simmer. Add the onions, leeks, celery, and carrots to the pot and saute until soft. Add the mushrooms, stir, and cover. Cook until the mushrooms have reduced and released their liquids. Uncover, and scootch the mushrooms and vegetables to clear an area. Add the tomato paste, and let it heat for a minute or two (it might darken - that's good). Stir the paste into the mushroom mixture, and add the remaining vegetable stock and lentils.

If it's been 30 minutes, drain the adzuki beans and transfer them to the soup pot to continue cooking.

Strain the porcini broth through a coffee filter, and add the strained broth to the soup. Chop the porcinis and add them, too.

Adjust heat to retain a gentle simmer (uncovered), and cook for 20 minutes. (Lentils need to cook for a minimum of 20 minutes; adzuki for 60 minutes total.)

Add a splash of shoyu or soy sauce and a big squeeze of lemon. Taste, and add salt by the pinch to suit.

Ladle into bowls and garnish with tarragon.