Until translucent

"Until translucent" tells you to cook onions, shallots, celery or leeks until they lose their white, raw look and turn soft and partly see-through. They should not brown. It is a common first step for soups, stews, risotto and sauces, building a sweet, mellow base. Cooking vegetables this way is also called sweating.

How to do it

1. Cut the onions evenly so they cook at the same rate.
2. Heat oil or butter in a pan over medium-low heat.
3. Add the onions with a pinch of salt. The salt draws out water and helps them soften.
4. Stir every minute or two.
5. Cook for 8 to 10 minutes for diced onion, until soft and glassy. A large batch takes longer.
6. If they start to brown at the edges, lower the heat and add a splash of water.

How to tell it is done

• The onion pieces look shiny and glassy, and you can see a little light through them.
• They bend and squash easily when pressed with a spoon.
• They smell sweet, with no sharp raw-onion bite.
• There is little or no browning.

Why it works

Gentle heat breaks down the cell walls of the onion and lets water escape, so the pieces turn soft and clear. Sharp sulfur compounds cook off and natural sugars come forward. Keeping the heat low means the water evaporates slowly and the surface stays below browning temperature. Higher heat would color and caramelize them, which gives a deeper, different flavor.

Common mistakes

• Heat too high. The outside browns and the inside stays crunchy.
• Rushing. Recipes often say 3 to 5 minutes, but most onions need closer to 8 to 10 to be truly soft.
• A crowded pan with too little fat. The onions steam unevenly and stick.
• Adding garlic at the start. It burns before the onions are ready. Add it in the last minute, until fragrant.

In recipes

"Cook the onion until soft and translucent" is the usual phrase. "Sweat the onions" means the same, often with a lid on. "Until softened" is close. A base of onion, carrot and celery cooked this way is a mirepoix or, in Italian cooking, a soffritto. Recipes that want color say "until golden" or "until caramelized" instead.