Bring a large pot of water with bay leaf, parsnips and potatoes to a boil. Cook vegetables until tender. Drain vegetables And return to warm pot. Using electric beaters, mash up vegetables and then beat in butter and cream. Season to taste and transfer to a flameproof casserole dish and create peaks with a spoon. Top with grated Parmesan and paprika. Bake for 30 minutes and brown under broiler.