Heat water in a saucepan and cook cauliflower until just tender but not overcooked - it should still have bite. Drain, reserving liquid.
In a second saucepan melt the butter, add the flour and fry to form a roux, stirring constantly. When the flour just begins to brown, pour in the cauliflower liquid, whisking constantly to dissolve lumps.
Season to taste with salt, pepper, seasoning, sugar, cream and plenty of nutmeg. Add the cauliflower florets back to the soup and reheat. Serve.