Hearty Lentil Stew

Hearty Lentil Stew Ingredients: 1 cup dried green or brown lentils, rinsed and drained 2 tablespoons olive oil 1 large onion, diced 2 carrots, diced 2 celery stalks, diced 3 cloves garlic, minced 1 (14.5-ounce) can diced tomatoes 6 cups vegetable broth 1 teaspoon dried thyme 1 teaspoon dried oregano 1 bay leaf Salt and pepper to taste 2 cups fresh spinach or kale, chopped 1 tablespoon red wine vinegar (optional) Fresh parsley, chopped for garnish (optional)