Winter Vegetable Soup

Ingredients

• 2 teaspoons extra virgin oil
• 1/2 pound leeks, trimmed, split in half lengthwise, and well rinsed
• 1 medium white onion, chopped
• 1/2 pound carrots, thinly sliced on the diagonal
• 2 large celery ribs, thinly sliced on the diagonal
• 2 tablespoons dried lentils, rinsed and picked over
• 2 tablespoons dried split peas, rinsed and picked over
• 2 tablespoons dried small white beans, rinsed and picked over
• 1 teaspoon dried thyme
• 1/2 teaspoon freshly ground pepper
• 2 quarts fat-free, reduced-sodium chicken or vegetable broth
• One 14 1/2-ounce can no-salt-added plum tomatoes, drained and coarsely chopped
• 1/4 pound spinach, tough stems discarded