Immune Boosting Vegetable soup with Parmesan Cheese

Ingredients

• 2 cups chopped onion (1 medium)
• 3 tbsp olive oil
• 1 ½ cups chopped carrot (3 to 4 carrots)
• 1 ½ cups chopped celery (2 to 3 stalks)
• 2 tbsp tomato paste
• 4 tsp minced garlic (4 cloves)
• 1 tsp ground fennel seed
• 1 tsp ground black pepper
• 1 tsp fine sea salt, plus more to taste
• ½ tsp crushed red pepper flakes
• 1 can diced tomatoes with their liquid (optional)
• 6 cups vegetable stock
• 2 cups chopped potato (2 medium)
• 3 to 4 cups(heaped) cabbage chopped or shredded
• 2 bay leaves
• 1 cup frozen peas (optional)
• a handful of shredded spinach
• ½ tsp apple cider vinegar or fresh lemon juice, optional
• The rind of parmesan cheese
• Grated parmesan