Trim chicken and season with salt, pepper, paprika, and onion powder and arrange in a 6 quart slow cooker. In a medium bowl, whisk together the sour cream, condensed cream of mushroom soup, chicken broth, minced garlic, and flour and until fully combined. Stir in the fresh sliced mushrooms. Pour the mushroom sauce over the chicken. Cover and cook for 4 hours on HIGH or 6 hours on LOW. Garnish with fresh minced parsley (optional) before serving.