Peel and chop the parsnips, then peel the onion and cut into 8 wedges and add them to the baking sheet along with the garlic cloves.
Drizzle with the oil and sprinkle with the curry powder, cayenne, salt and pepper, then toss it all together to coat. Spread it out on the tray, but don’t overcrowd the vegetables. You may need two trays. Roast for 25 minutes or until soft.
Remove some of the roasted parsnips for garnish, then put the rest of the roasted parsnips, onion and garlic into a blender (don’t overfill) along with the vegetable stock and butter. You may need to do this in batches. Whiz until smooth.
Add it back to the pot and reheat. Stir in the lemon juice.
Serve garnished with the reserved roasted parsnips.
Chop the parsnips all to roughly the same size to ensure that they all cook evenly and are finished roasting at the same time.
Roast whole garlic cloves and large onion wedges to keep them from overcooking or burning while roasting.
When roasting the vegetables, make sure everything is in a single layer to prevent them from steaming. This may mean that you need to roast the veggies on two different baking sheets.
When blending the hot soup, do not overfill the blender as it can spill out and become dangerous. Blend in batches if needed.
Before blending, reserve some roasted parsnips to garnish the final dish.
When purchasing parsnips at the grocery store or farmers’ market, make sure they are firm and strong with no bruising.