A clear winner: what is brown butter and how do I use it?

What's the deal with brown butter? I keep seeing it in recipes and on menus.

- Ben, Sheffield

Achieved by heating butter until the water evaporates and the milk solids caramelise, brown butter (or beurre noisette) can enhance the flavour of all the good things - cookies, cakes, pasta, pork chops. "It can be a beautiful thing," agrees baker Lily Jones, of Lily Vanilli in east London, who recently launched an initiative across the capital to get birthday cakes to those who would otherwise go without. "It has a subtle, nutty, toffee caramel flavour that brings extra sweetness and richness."