Step 1

Wash and dry the onions, then remove the onion skins and set them aside. Thinly slice the onions.

Step 2

Heat the olive oil in a large stock pot over medium heat. Add the onions, shiitake stems, and cremini mushrooms and cook, stirring occasionally, for 10 minutes, or until the onions are soft and browned.

Step 3

Add the water, onion skins, garlic bulb, ginger, dried mushrooms, tamari, and peppercorns. Bring to a boil over high heat, reduce the heat to low, and add the kombu. Cover and simmer for 1 hour. Strain and season to taste.