Bake the parsnip, sweet potato, cauliflower, onion and garlic for approximately 45 minutes at 180 degrees C / 350 degrees F. No oil is required because we want to cook them but not turn them golden, or it will not remain white. If they start to colour, cover with a sheet of parchment paper.
Once cooked, place the cooked vegetables in a large pot. Remove the garlic bulbs from the skin before adding.
Add all the remaining ingredients to the pot and simmer for approximately 15 min.
Season well.
Puree the soup in the pot then serve with some fresh thyme leaves sprinkled on top.
Pan fry bacon until crispy, and add on top of each serving.
Notes
If you can't find parsnip, swede and turnip add a nice flavour as well.