Caramelized Onions

Name: Caramelized Onions
Prep time: 15 min
Cook time: 45 min
Total time: 1 h
Ingredients: 1½ kg (3¼ lb) yellow onions, about 6 large, halved and thinly sliced from root to tip; 30 g (2 tbsp) unsalted butter; 2 tbsp olive oil; 5 g (¾ tsp) fine sea salt; 60 ml (¼ cup) water, plus more as needed; 1 tsp sherry vinegar or balsamic, optional

An hour of patience for the sweetest, deepest onions

Makes: about 300 g (1¼ cups)
Hands-on: 15 min
Total: 1 h
Level: Easy

True caramelized onions are cooked slowly until they collapse into a soft, jammy, mahogany tangle. They take time, but they keep for a week and transform burgers, soups, tarts and sandwiches.

Ingredients

1½ kgyellow onions (3¼ lb)about 6 large, halved and thinly sliced from root to tip
30 gunsalted butter (2 tbsp)
2 tbspolive oil
5 gfine sea salt (¾ tsp)
60 mlwater (¼ cup)plus more as needed
1 tspsherry vinegar or balsamicoptional

Diet: Vegetarian, Gluten-free
Allergens: milk, sulphites

Method

Heat the butter and oil in your widest heavy pan (at least 28 cm) over medium heat until foaming.
Add the onions and salt. They will mound up; stir to coat, cover, and cook for 10 minutes, stirring once, until they have softened and released liquid.
Uncover and cook over medium-low heat, stirring every 3–5 minutes, for 35–45 minutes. As brown bits form on the pan, add a splash of water and scrape them up. 40 min
The onions are done when they are soft, jammy and the color of dark caramel, reduced to about a fifth of their original volume.
Stir in the vinegar if using, and taste for salt.

Why it works

Slow cooking first breaks down the onions' cell walls and evaporates water, then lets sugars caramelize and proteins undergo Maillard browning together; high heat would scorch the outside before the inside softened. Deglazing with small splashes of water dissolves the browned layer on the pan and folds it back into the onions, so they color evenly and deeply. Salt at the start draws out moisture and speeds the softening.

Common mistakes

Cranking the heat to save time: you get burnt edges and raw centers. It takes at least 45 minutes.
Crowding a small pan: they steam. Use a wide pan or cook two batches.
Stopping at golden: that's sweet, not caramelized. Go to deep brown.

Variations

Balsamic onion jam: Add 2 tbsp brown sugar, 2 tbsp balsamic and a thyme sprig for the last 10 minutes.

Make ahead and storage

Keeps 1 week in the fridge, 3 months frozen in small portions.

Notes

Use them in French Onion Soup, on burgers, in Frittata, or stirred into Gravy. Use all oil for a dairy-free version. Sulphites only if you add the vinegar.