Fudgy brownies

Method

1. Heat the oven to 180°C (160°C fan). Grease a 20cm square tin, at least 4cm deep, and line it with baking paper, leaving some overhanging on two sides so you can lift the brownies out later.
2. Put the chocolate and butter in a heatproof bowl set over a pan of barely simmering water, without the bowl touching the water. Stir now and then until the last pieces have just melted and it is smooth and glossy, 4 to 6 minutes. Take the bowl off the heat and leave it to cool while you whisk the eggs, since too hot a chocolate scrambles them.
3. In a large bowl, whisk the sugar, eggs and vanilla with an electric whisk on high for 5 to 7 minutes, until pale, thick and roughly doubled. When you lift the beaters, the trail should sit on the surface for a moment. This is what gives you the shiny, crackly top. By hand with a balloon whisk it takes about 10 minutes and gets a little less thick.
4. Pour in the melted chocolate and fold it through gently with a spatula until there are no streaks left. Fold rather than beat, to keep the air you just whisked in.
5. Sift the flour, cocoa and salt over the bowl and fold only until you can no longer see any flour, then fold in the chocolate chips or nuts if using. Stop there, since overmixing makes brownies cakey.
6. Scrape into the tin and level the top. Bake for 25 to 28 minutes, until the top is shiny and crackled and the edges are set but the middle still has a slight wobble. A skewer in the centre should come out with moist crumbs, not wet batter. They keep cooking as they cool.
7. Leave to cool completely in the tin, at least 1 hour, or chill for 30 minutes after that for the cleanest cuts. Lift out and cut into 16 squares with a hot knife wiped between cuts. Serve as they are, or warm a square in the microwave for 10 to 15 seconds and add a scoop of vanilla ice cream.