Heat your oven to 200°C/Fan 180°C/Gas 6. Peel the potato, parsnip and carrots. Slice them into chips about as long as a little finger. Pop them in a bowl. Add ½ tbsp olive oil and a pinch of salt and pepper.
Toss to mix.
Spread the vegetable chips out on a baking tray in a single layer. Roast for 10 mins on the top shelf of the oven.
Separate the egg and pour the egg white onto a lipped plate (see our tip on what to do with the egg yolk). Whisk to break it up. Shake the polenta onto a separate plate. Finely chop the chives and add most of them to the polenta. Season with a pinch of salt and pepper. Line a baking tray with baking paper.
Dip the whiting fillets in the egg white to coat them, then dip them in the polenta till they’re covered all over. Lay on the baking tray.
Move the chips down to the middle shelf in the oven. Put the fish on the top shelf. Bake for 25 mins till the fish is golden and cooked through and the chips are tender and a little charred.
Arrange the fish and chips on two warm plates. Scatter over the remaining chives and serve with lemon wedges for squeezing.