Washed the King Oyster Mushrooms and cut the cap from the top. Then trim the ends of the stems. Using the tines of a fork, shred the stems of the mushrooms lengthwise. They should take on the appearance of pulled meat. Then thinly slice the caps.
Add the shredded mushrooms and red wine to a large, deep-sided cast iron skillet. Bring to a simmer and allow the wine to cook down. 8-10 minutes.
When the wine has almost completely cooked off, add 2 tbsp of extra virgin olive oil and sauté the shredded mushrooms until they just begin to brown. About 2-4 minutes.
Add the diced onions and salt and reduce the heat to low. Slow cook the mushrooms and onions, stirring occasionally, allowing the onions to caramelize slightly. About 20 minutes. Be careful not to burn the onions.
While the onions are sautéing, combine the tamari, maple syrup, balsamic vinegar and smoked paprika in a small bowl. Set aside.
Increase the heat to medium and add the minced garlic. Sauté for 1-2 minutes. Add the dried parsley and thyme and tomato paste. Stir to combine and continue to cook until the tomato paste becomes a dark red. About 2-3 minutes
Add the tamari mixture and continue to cook until the mixture has reduced. About 3-4 minutes.
Add the carrots, celery, soaked Great Northern Beans, sun-dried tomatoes, vegetable broth and water (but see Recipe Notes if you are using canned beans in lieu of dried beans).
Reduce the heat and allow the dish to simmer slowly until the broth has reduced to a thick stew. About 1 hour. See Recipe Notes if you are using canned Great Northern Beans.
Preheat oven to 325º.
When the cassoulet has a thick, stew-like consistency, put the cassoulet on the middle rack of the oven and bake for ~30 minutes. After 30 minutes, the top of the cassoulet should have developed a crust. Gently break a small spot in the crust and spoon the sauce from underneath over the top of the crust then bake for an additional 30 minutes. Allow to cool slightly, then serve.