Winter Lentil Soup

INGREDIENTS

• 4 leeks, white and light green parts only
• 1 bunch kale
• 1 tablespoon olive oil
• 1 28-ounce can whole tomatoes, drained
• 6 cups water
• 2 sweet potatoes, peeled and cut into a 1/2-inch dice
• 1/2 cup brown lentils
• 1 tablespoon fresh thyme leaves
• 2 teaspoons kosher salt
• 1/4 teaspoon black pepper
• 12 fresh basil leaves (optional)
• 1/4 cup (1 ounce) grated Parmesan (optional)