Sauté diced onion in olive oil in a large pot over medium heat until onion is translucent (about 3-4 minutes)
Add carrots, celery, mushroom and garlic. Sauté for another 2-3 minutes.
Add flour, salt, pepper, thyme and oregano. Mix to combine so that the vegetables are well coated in flour. If there are lumps, that's okay.
Add vegetable stock, plant-based milk, white navy beans, and brown rice if using uncooked. Bring soup to a low boil, then reduce heat to low and cover. Simmer for 20-25 minutes until carrots are fork tender and brown rice is cooked (if using uncooked brown rice).
Add kale, lemon juice, balsamic and brown rice (if using cooked). Cook until kale is wilted (about 3 minutes), serve and enjoy.