1. Pre-heat the oven to 220C/425F/gas mark 7. Peel the parsnips, potatoes, red onion and garlic. Slice the parsnips and potatoes into long strips and chop the onions into chunky quarters. Roughly chop one of the garlic cloves.
2. Place the prepared vegetables in a baking tray and cover with 2 tbsp of olive oil. Season with salt and freshly ground black pepper and roast for 40 minutes.
3. While the vegetables are roasting, prepare the salmon. Season the fillets on both sides with salt and pepper, and rub some butter on to the skin. Spoon the flour on to a plate and place the fillets on top, skin-side down.
4. Heat 1 tbsp of olive oil in a frying pan and add the salmon skin-side down. Cook for 4 minutes, turning the salmon after 2 minutes. When the vegetables have 10 minutes left in the oven, place the salmon inside and at the same time give the roasting vegetables a stir, adding more olive oil if necessary.
5. After 10 minutes, remove the salmon and vegetables. Stir 1 tbsp balsamic vinegar through the vegetables.
6. Finely chop the remaining garlic clove and shred the basil by hand. Place in a dish and mix with a generous amount of olive oil, salt and freshly ground pepper to make a basil oil dressing.
Tip: Stack the vegetables on top of one another, with the red onion chunks on either side. Place the salmon fillet on top of the vegetables and drip basil oil over the top.