Slow Carb Cabbage Soup

This recipe makes 8 cups

2 T olive oil
2 small leeks - white part only cleaned and chopped
2 medium onions - diced
2 T chopped garlic
4 c chicken stock
2 c water
2 large carrots - peeled and chopped
3 parsnips - peeled and chopped
2 cups green cabbage - shredded
1 tsp salt
1/4 tsp black pepper
1/4 c chopped fresh parsley