Slow-Cooker Lentil & Root Veggie Soup

Ingredients

• 3 cups chopped, peeled celeriac (celery root)
  
• 2 cups chopped parsnips
  
• 1 cup chopped carrot
  
• 1 cup frozen pearl onions
  
• 1 stalk celery, chopped
  
• 2 plum tomatoes, seeded and chopped
  
• 3 cloves garlic, minced
  
• 2 teaspoons herbes de Provence
  
• 8 cups vegetable broth
  
• 1 cup French green lentils or black lentils, rinsed
  
• 1 sprig fresh rosemary
  
• 1 (3-inch) Parmesan cheese rind
  
• ¹/₂ cup grated Parmesan, divided
  
• 1 bay leaf
  
• 1 teaspoon salt
  
• ¹/₂ teaspoon ground pepper
  
• 4 ounces pancetta, crisp-cooked and crumbled (optional)