Mist a large pan with cooking spray and fry the shallots over a medium-high heat 5 minutes until starting to soften. Add the oregano and cook 1 minute.
Add the cauliflower and stock. Cover and bring to the boil, then reduce the heat and simmer 15 minutes until the cauliflower is tender.
Transfer half of the cauliflower to a bowl using a slotted spoon. Add half the Stilton to the soup, then use a stick blender to blitz until smooth. Season to taste.
Return the reserved cauliflower to the soup with most of the parsley. Divide between bowls and scatter over the remaining Stilton and parsley. Serve with the toast.