Scrub the parsnips, then blanch whole in a large pan of boiling salted water for 5 minutes, then drain and steam dry.
Tip into a large roasting tray, dot over the butter and a pinch of sea salt and black pepper, toss to coat and arrange in a single layer, then roast for 1 hour.
Remove the tray from the oven, quickly scatter over the bay leaves and drizzle with the vinegar and honey, then toss together and roast for a final 10 minutes, or until beautifully golden.
