To prepare a vegan mushroom thanksgiving stuffing recipe, first you will need to gather your ingredients. You can find mushrooms at your local grocery store, or you can buy them online. Cut the mushrooms in half lengthwise, and then cut them into quarters. Place the quartered mushroom halves into the crock pot. Cover the pot and cook on medium heat, stirring occasionally, until they are soft and browned, about 30 minutes. Remove the pan from the heat and add the chopped parsley. Season with salt and pepper to taste.