How do you brown butter, and what do you use it for?

Brown butter is ordinary butter taken a step further, and that step makes a remarkable difference. It goes from creamy and mild to nutty, toasty and deep, with a smell that makes people wander into the kitchen to ask what's cooking.

What it is

The French call it beurre noisette, hazelnut butter, after its colour and smell. As Wikipedia's beurre noisette article explains, when butter melts it separates into fat and milk solids; the solids sink and, as you keep heating, toast until they reach a hazelnut colour. Those toasted specks are where the flavour lives. Cook it further and you get beurre noir, darker again, which is a different sauce.

How to do it

The pan

Use a light-coloured pan, stainless steel rather than black non-stick or cast iron, so you can actually see the colour change. A small frying pan or saucepan is ideal.

The stages

1. Melting. Cut the butter into pieces and melt it over medium heat.
2. Foaming. It bubbles and foams as the water cooks off. It also crackles. Keep swirling the pan.
3. Quieting. The crackling settles and the foam becomes finer. Look underneath it: small specks are forming on the bottom of the pan.
4. Browning. The specks turn from pale gold to amber to hazelnut brown, and the butter smells of toasted nuts and caramel. This is the moment.

The moment before burning

Brown butter turns into burnt butter quickly. As soon as the specks are golden-brown and it smells nutty, take the pan off the heat and pour the butter into a heatproof bowl, specks and all. Leaving it in the hot pan keeps it cooking.

Signs you've gone too far: black specks, a bitter, acrid smell, smoke. Then it is better to start again; burnt butter tastes burnt in everything.

The Italian classic: burro e salvia

Butter and sage is one of the simplest and best sauces we know, especially for filled pasta like ravioli and tortelli, and for potato gnocchi (see why gnocchi go gummy).

Brown the butter as above, and when it is foaming, add whole sage leaves. They sizzle and crisp in the butter, and their flavour goes into it. When the butter is nut-brown and the leaves are crisp, take it off the heat. Toss with the drained pasta and a splash of its cooking water, then finish with plenty of grated Parmesan.

More ways to use it

• Over vegetables: roasted squash or pumpkin, steamed green beans, asparagus, cauliflower. With squash it is particularly good; see butternut squash.
• With eggs: spooned over fried or poached eggs, or used to cook scrambled eggs.
• With lemon: a squeeze of lemon into brown butter makes a quick sauce for pasta, vegetables or fish. Take care, it spits.
• With nuts: toast hazelnuts, almonds or pine nuts in it.
• In baking: Wikipedia notes it is a common ingredient in French pastries such as madeleines and financiers. It also makes biscuits and cakes taste deeper and richer. Let it cool before using.
• On popcorn: salted, unreasonably good.

Tips

• Salted or unsalted? Unsalted gives you more control, especially for baking. Salted works fine for savoury sauces; just taste before adding more salt.
• Make a bit extra. Brown butter can be cooled, chilled and used later; it solidifies and keeps its flavour.
• Scrape in the specks. They are the best part. Don't strain them out unless a recipe demands it.