Best brownies

Butter an 8x8 baking dish and line it with parchment.

Mix the flour with the kosher salt.

Chop the unsweetened chocolate into a heatproof bowl with the butter and set it over a couple of inches of barely simmering water on the lowest heat until melted and smooth, then turn off the heat.

Beat the eggs and sugar on high speed for four or five minutes until light, airy and very creamy.

Mix in the vanilla, then drizzle in the melted chocolate and butter and mix on high until thick and airy.

Add all the flour at once and mix on low only until it disappears, then scrape into the prepared dish and push it into the corners.

Bake in the centre of a 350 degree oven about 30 minutes, until a skewer poked in two inches from the centre comes out clean.

Cool on a rack for exactly 15 minutes, then press lightly around the raised outside edge to even the thickness.

Cool fully to room temperature, lift out, and cut with a long thin serrated knife, cutting through the crusty edge before finishing the cut.