Heat the butter in a heavy pan over a low to medium heat. Add the garlic, onion, parsnips and potatoes and sweat, covered for about 10 minutes, shaking the pan occasionally.
Add the curry powder to the vegetables and cook for a couple more minutes before gradually adding the stock. Simmer until the parsnips are tender.
Liquidise or process the vegetables then return to the pan. Dilute with water if needed and season to taste.
Pour in the cream and reheat without boiling. Scatter with chives and parsley and serve with croutons of bread fried in butter.