Roasting
Cooking Skills: Vegetables 1
Chapter 3 · Roasting
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The basics
Roasting cooks vegetables in dry heat. The surface dries and browns, and the browning (a set of reactions that create new flavours) turns vegetables sweet and savoury. A roasted carrot tastes quite different from a boiled one. There are only four things to control: temperature, size, space and oil.
What makes a good roast
- A hot oven, usually 200°C (180°C fan), or 220°C (200°C fan) for brassicas and thin pieces. Too cool and the vegetables dry out without browning.
- Even pieces, so that everything is done at the same time. Smaller pieces cook faster and brown more.
- One layer, with space. Overcrowded vegetables give off steam that can't escape, so they stew instead of roasting.
- Just enough oil: roughly 1 tablespoon for each 400 g to 500 g of vegetables, tossed in a bowl so each piece is lightly coated. Too little and they scorch; too much and they're greasy.
- Dry vegetables. Wash them ahead and pat dry.
- Turn once, halfway through.
- A big tray, with low sides so that air circulates.
Roughly how long?
| Vegetable | Cut | Oven | Time |
|---|---|---|---|
| Carrots, parsnips | 2 cm batons | 200°C (180°C fan) | 35 to 45 minutes |
| Butternut squash | 2 cm chunks | 200°C (180°C fan) | 25 to 35 minutes |
| Beetroot | 2 cm chunks, peeled | 200°C (180°C fan) | 35 to 45 minutes (wear gloves: it stains) |
| Cauliflower, broccoli | Florets | 220°C (200°C fan) | 20 to 25 minutes |
| Brussels sprouts | Halved | 220°C (200°C fan) | 20 to 25 minutes |
| Courgette, aubergine | 3 cm chunks | 200°C (180°C fan) | 25 to 30 minutes |
| Peppers, onions | Strips or wedges | 200°C (180°C fan) | 25 to 35 minutes |
| Whole tomatoes (slow) | Halved | 180°C (160°C fan) | 35 to 45 minutes |
These are starting points. Ovens vary, so check a minute or two before the time, and test with a knife.
Seasoning
Salt and pepper and a herb are enough. Add a little acid at the end (lemon juice, vinegar) to lift the flavour, and fresh herbs at the end, as they burn if roasted for a long time. Spices (cumin, paprika, coriander) are good with squash, cauliflower and carrots.
Try it
Roast root vegetables
The simplest roast, and the one that teaches the most. Set the oven to 200°C (180°C fan).
Ingredients (2 portions)
- 2 carrots
- 2 parsnips
- 1 red onion, in wedges
- 1½ tbsp oil
- 3 sprigs thyme (or 1 tsp dried)
- 1 pinch salt and pepper
- Scrub or peel the carrots and parsnips and cut into pieces of the same thickness (batons about 2 cm thick). Cut any thick parsnip tops in half lengthways.
- Toss in a bowl with the oil, salt, pepper and thyme, so that every piece is lightly coated.
- Spread in a single layer on a large tray, with space between pieces. Add the onion.
- Roast for 35 to 45 minutes, turning once halfway, until tender inside and golden at the edges.
Roast cauliflower, broccoli and sprouts
Roasting brings out sweetness in brassicas and removes the cabbage smell that comes from overcooking. Set the oven to 220°C (200°C fan), a bit hotter than for roots.
Ingredients (3 portions)
- ½ cauliflower, in florets
- 1 head of broccoli, in florets
- 150 g Brussels sprouts, halved
- 1½ tbsp oil
- 1 tsp ground cumin or paprika (optional)
- ½ lemon, juice only
- 1 pinch salt and pepper
- Cut everything to similar-sized pieces. Dry the vegetables well after washing, as damp pieces steam.
- Toss with the oil, spice, salt and pepper and spread on a large tray, cut sides down where you can.
- Roast for 20 to 25 minutes, turning once, until the cut sides are golden and the stalks are tender.
- Finish with the lemon juice.
Roast tomatoes and peppers
A lower oven (180°C, or 160°C fan) and a longer time turns tomatoes and peppers soft, sweet and jammy. Good on toast, in pasta, or blitzed into a soup.
Ingredients (2 portions)
- 300 g ripe tomatoes (cherry or plum)
- 2 peppers, in strips
- 2 garlic cloves, in their skins
- 1 tbsp oil
- 1 tsp dried oregano or fresh thyme
- 1 pinch salt and pepper
- Halve plum tomatoes (cherry ones can stay whole). Put them cut side up on a tray with the pepper strips and unpeeled garlic.
- Drizzle with oil and sprinkle with salt, pepper and herbs.
- Roast for 35 to 45 minutes, until the tomatoes have collapsed and the pepper edges are lightly browned.
- Squeeze the soft garlic out of its skin and mash it into the tomatoes.
A tray of mixed roast vegetables
Different vegetables roast in different times. The skill is to cut the slow ones smaller, or start them first, so everything finishes together. Set the oven to 200°C (180°C fan).
Ingredients (3 portions)
- 1 courgette, in thick slices
- 1 red pepper, in chunks
- 1 small aubergine, in chunks
- 150 g butternut squash, peeled, in 2 cm chunks
- 1 red onion, in wedges
- 2 tbsp oil
- 1 tsp mixed herbs
- 1 pinch salt and pepper
- Cut the squash into 2 cm chunks, the aubergine and pepper into 3 cm chunks, and the courgette into thick slices. Keep everything about the same thickness.
- Toss the squash and onion with a third of the oil, salt and pepper and spread on 2 trays. Roast for 10 minutes.
- Toss the rest of the vegetables with the remaining oil and herbs. Add them to the trays, with spaces between.
- Roast for a further 25 to 30 minutes, turning once, until everything is tender and browned in places.
Experiments
Oven temperature
Cooler or hotter.
- Roast the same cut carrots on two trays: one at 160°C (140°C fan) and one at 220°C (200°C fan), for 30 minutes.
- Compare colour, texture and sweetness.
Look for: The cooler tray is softer and paler; the hotter tray browns faster, with a crisper edge. Watch the hotter one: it can go from golden to dark brown quickly. Aim for golden.
Crowded or spaced
Steam versus roast.
- Put half a tray of cauliflower florets tightly packed on one tray, and the same amount spread out on another.
- Roast both at 220°C (200°C fan) for 20 minutes.
Look for: The crowded tray comes out paler and softer, the spaced tray golden at the edges.
How much oil
None, a little, a lot.
- Toss 3 batches of carrot batons with no oil, 1 teaspoon of oil, and 1 tablespoon of oil per 200 g.
- Roast all together at the same temperature.
Look for: No oil gives dry, leathery vegetables; a little gives a good colour; a lot gives greasy ones.
Covered or uncovered
Foil on, foil off.
- Roast two trays of squash chunks, one covered tightly with foil for 15 minutes then uncovered for 15, and one uncovered for 30.
Look for: The covered tray starts steaming, so it is softer inside; the uncovered tray browns more. Covering is useful for tough vegetables that need to soften before they brown.
Tasting notes
| What I tried | Method or amount | What I saw | What I thought | Will I do it again? |
|---|---|---|---|---|
| Roast root vegetables | ||||
| Roast cauliflower, broccoli and sprouts | ||||
| Roast tomatoes and peppers | ||||
| Tray of mixed roast vegetables | ||||
| Oven temperature | ||||
| Crowded vs spaced | ||||
| Oil amount | ||||
| Covered vs uncovered |
Troubleshooting
| Problem | Likely cause | What to do |
|---|---|---|
| Pale and soft | Crowded tray, damp vegetables, or oven too cool | Use 2 trays; dry well; raise the temperature |
| Burnt outside, hard middle | Too hot, or pieces too big | Lower the oven; cut smaller |
| Dark brown or black edges | Too hot or too long | Take out earlier; aim for golden (see the box) |
| Greasy | Too much oil | Use less; blot on kitchen paper |
| Sticking to the tray | Too little oil, or turned too soon | Leave until golden before turning; line the tray with baking paper |
Go for gold. Carrots, parsnips and other starchy vegetables form a chemical called acrylamide when roasted or fried at high temperatures. The Food Standards Agency's advice is to cook them to a golden yellow, not dark brown.
Knife safety: cut on a stable board (a damp cloth underneath), tuck your guiding fingertips back (the claw), and cut round or slippery vegetables on a flat face so they can't roll. A sharp knife is safer than a blunt one. Never catch a falling knife. Cooking Skills: Knife Skills 1 covers all of this.
Leftovers: cool cooked vegetables quickly (within 1 to 2 hours), keep them covered in the fridge, and eat within 2 days. Reheat until steaming hot all the way through, and only once.
- I roast at the right temperature for the vegetable.
- I cut pieces evenly and spread them in one layer.
- I use just enough oil and dry the vegetables first.
- I can combine slow and fast vegetables on one tray.
- I cook to golden, not dark brown.