How do you make a light, crisp batter for frying vegetables?

A heavy batter feels like a blanket. A light one shatters when you bite it, and the vegetable inside is still juicy. The difference is mostly about gluten, temperature and restraint.

Why cold, and why lumpy

Wheat flour contains proteins that form gluten when you add water and mix. Gluten is great for bread and terrible for batter. The more you mix, the more gluten develops, and the batter becomes chewy and bready when it fries. Wikipedia's tempura entry describes the Japanese approach: batter mixed briefly with chopsticks, leaving lumps, using iced water and soft, low-gluten flour, and kept cold, sometimes over ice. Overmixing, it notes, makes the batter go soft and doughy when fried.

That is the whole secret, really. Cold slows gluten down; minimal mixing gives it no chance to form.

The sparkling water trick

The same tempura article notes that sparkling water instead of still has a similar lightening effect. The bubbles help aerate the batter as it hits the hot oil. Keep a bottle in the fridge, and open it just before mixing.

Flour choices

• Plain flour works well, especially mixed with a little cornflour or rice flour.
• Rice flour on its own gives a very crisp, delicate coating and has no gluten at all.
• Italian "00" flour is common in Italian frying batters.

A little baking powder can lighten things further. A pinch of salt in the batter seasons the coating.

Make it at the last minute

Batter does not like to wait. Have the oil heating, the vegetables prepped and dry, a tray with a rack ready, then mix. Make it in small batches if you are frying a lot: a fresh, cold batter for the second round beats a warm, tired one.

Frying well

• Dry vegetables. Pat everything completely dry. Water makes the batter slide off and the oil spit.
• A light dusting of flour on the vegetables first helps the batter cling.
• Hot oil. Drop in a little batter: it should sizzle immediately and float. Too cool and the batter absorbs oil; too hot and it browns before the vegetable cooks.
• Small batches. Overcrowding cools the oil.
• Pale gold is the cue. Light batters stay pale and crisp rather than turning deep brown.
• Drain on a rack, not on a flat pile of paper, where the steam softens the underside. Salt immediately.

Use a deep, heavy pan, never fill it more than about a third with oil, keep children and pets away, and never leave hot oil unattended.

What to fry

Italy has its own long tradition of battered vegetables. Wikipedia's fritto misto entry mentions fritto misto di verdure with artichokes and mushrooms, and lists cauliflower, courgettes and their flowers and aubergines among the vegetables used across regions. Our favourites:

• Courgette flowers, stuffed or plain. See courgette flowers.
• Courgette batons and thin slices of aubergine.
• Sage leaves, fried whole, an excellent snack with drinks.
• Cauliflower and broccoli florets, blanched first so they cook through.
• Fennel wedges, thin onion rings, artichoke hearts and mushrooms.
• Thin slices of squash or sweet potato.

Serve with lemon wedges and flaky salt, and eat them straight away. Fried food waits badly.