Heat olive oil in a large heavy frying pan big enough to hold all the ingredients.
Add onion, garlic, thyme, fennel (affiliate link), and sage and cook, stirring a few times, until the onions are softened and starting to brown. This will take about 8 minutes.
While onions cook wash mushrooms, trim off woody stems, and cut mushrooms into quarters or sixths.
When onions are slightly browned, add mushrooms and ¼ cup vegetable stock, and let simmer covered for 5-6 minutes, until mushrooms have shrunk somewhat and released their juice. (See note about reducing the vegetable broth for best flavor.)
While mushrooms cook. drain the beans into a colander placed in the sink and rinse with cold water until no more foam appears.
After mushrooms have cooked 5-6 minutes, add drained beans, tomatoes and juice from the can, and ½ cup chopped parsley to the pan.
Cover again and simmer 10 minutes more.
After 10 minutes the stew should be slightly thickened and flavors should be well-blended.
Season to taste with salt and fresh ground black pepper.
Serve hot, over brown rice or cauliflower rice, or just in a bowl as a meatless stew.
