Prepare the Cabbage: Remove the core from the cabbage head and carefully separate the leaves. Trim the thick veins from the leaves.
Sauté the Vegetables: Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the baby Bella mushrooms, red bell pepper, red onions, and garlic. Sauté until the vegetables are tender and slightly caramelized.
Season the Filling: Sprinkle the herb de Provence or Italian spice mix, salt, ground pepper, smoked paprika, and nutritional yeast (if using) over the sautéed vegetables. Stir well to combine.
Prepare the Slow Cooker: Grease the inside of your slow cooker with 1 tablespoon of olive oil to prevent sticking.
Layer the Cabbage and Filling: Place a layer of cabbage leaves at the bottom of the slow cooker. Add a layer of the vegetable filling on top. Repeat the process, alternating between cabbage leaves and the filling until all the ingredients are used
Cook on Low: Cover the slow cooker and cook on low heat for 6-8 hours or until the cabbage is tender and the flavors have melded together.
Optional Cheese Topping: If desired, sprinkle vegan or regular cheese over the cabbage rolls casserole during the last 30 minutes of cooking. Close the slow cooker to allow the cheese to melt.
Serve: Carefully remove the cabbage rolls casserole from the slow cooker and transfer it to a serving dish. Sprinkle almond flour evenly over the casserole for a crunchy topping. Serve the hot bubbly casserole warm and enjoy!