Stir together the broth, lentils, carrots, onion, celery, rice, garlic, herbes de Provence, salt and pepper in a slow cooker. Cover and cook on low for 8 hours or on high for 4 to 5 hours. Remove 1 1/2 cups soup and puree in a food blender or with an immersion blender until almost smooth. Stir pureed soup back into the slow cooker.
Divide soup evenly among 4 serving bowls, garnishing each with 1 tablespoon cream and 1 tablespoon chopped parley, if desired.