1Pre-heat oven to 200 C. Divide cauliflower into small florets. Toss with olive oil to coat. Arrange cauliflower and halved garlic head on a baking sheet and roast for 30 minutes or until lightly golden on tops.
2Add to the prepared stock.
3Put olive oil in a medium pot over medium heat. Add the onion and cook until translucent and soft.
4Add the parsnip, celery and stock. Bring to a boil, reduce heat, and simmer.
5Add the cauliflower and simmer until soft, around 20 more minutes. Add the roasted garlic, after cooling slightly, by squeezing the head until the cloves pop out.
6Use an immersion blender and puree the soup for a minute until completely smooth.
7Add the milk, salt, pepper and grated parmesan on the top.