In a large pot, add the brown rice and vegetable stock, and bring it to a boil. Reduce the heat to low, cover the pot with a lid, and let it simmer for 40 to 45 minutes. Turn the heat off, and let the rice rest with the lid on for 5 minutes before taking the lid off and fluffing the rice with a fork.
While the rice is cooking, heat the olive oil in a skillet over medium heat. Add the onions, celery, mushroom, green onions, thyme, sage and sautée until the onions turn translucent. Add the jackfruit and garlic, and sautée for another couple of minutes.
Add the sautéed vegetables, nuts and cranberries to the rice, and stir. Taste for seasoning. Pour it into a casserole dish or large serving dish.