Melt butter in large stockpot. Add garlic and onion, cooking on low and stirring until soft. Add stock, cauliflower, celery root, and salt to taste. Simmer, covered, until vegetables are tender, adding more stock or dry white wine, as needed. Using a hand-held blender, process soup until smooth. And cream and gently heat through. Garnish with shavings of hard cheese or crumbles of softer cheeses, and snipped chives or parsley.