Melt the butter in a saucepan over low heat. Add the onion, garlic, thyme (if using fresh thyme) and bay leaf and cook for 5-8 minutes or until onion has softened. Add the cauliflower, potato, vegetable stock and milk, increase heat to medium and cook for 25-30 minutes or until cauliflower and potato is tender.
Alternatively finish this part of the cooking in the Microwave for about 10 minutes at 100% power. If using dried thyme, add at this point with the garam masala and mix well.
Remove from the heat and, using a mixer-blender/ hand-held blender, blend until smooth. Stir in the salt and pepper. Warm the soup before serving and garnish with Parmesan cauliflower crumbs and red chilli flakes if desired.
While the soup is cooking, make the Parmesan cauliflower crumbs. Place the cauliflower florets, olive oil and grated Parmesan in a bowl and toss to combine. Heat a non-stick frying pan over high heat. Put the cauliflower-oil-Parmesan into the hot pan and cook, stirring for 2 minutes or until golden and crisp. Top soup with cauliflower crumbs to serve.