In a large pot, add soaked wheat berries with 6 cups of water and kombu. Simmer covered for about 40 mins, or until most of the water is absorbed. Once cooked, remove kombu.
In a skillet, sauté onions in half the olive oil for a few minutes, then add salt,garlic, thyme and rosemary. Then add in the fennel, squash, potato and cabbage.
Cook for a few more minutes, then add the contents of the skillet into the pot with the wheat berries. Add veggie soup base to desired consistency, then cover with lid and bring to a boil and simmer for 10 minutes.
Reusing the now empty skillet, add the remaining olive oil to the pan and then stir in mushrooms. Add more salt and pepper to taste and cook for 5 minutes, or until mushrooms start to brown, then add to soup.
Cook stew for 10 to 15 more minutes, until flavors have combined. Serve warm.
Want to cook it in the Instant Pot? See Instructions above in blog post.