Turtle Brownies

Heat the oven to 175C (350F). Line a 23 cm square pan with parchment, leaving an overhang on two opposite sides so the slab lifts out cleanly.

Melt the butter with the chocolate chips in a saucepan over low heat, stirring constantly until smooth and glossy, then take it off the heat and cool for 5 minutes.

Tip: Keep the heat low and never stop stirring: overheated chocolate turns grainy and there is no recovering it.

Whisk the sugar into the warm chocolate, then the eggs one at a time and the vanilla, beating hard for a full minute after the last egg until thick and glossy.

Tip: That minute of hard whisking dissolves the sugar and gives you the papery crackled top.

Sift in the flour, cocoa and salt and fold with a spatula only until the dry streaks disappear. The batter will be very thick and slow to level.

Scrape the batter into the pan and spread it level into the corners. Bake for 20 minutes: it will be set at the edges and still soft in the middle.

Pull the pan out and press the Turtles gently into the surface in an even grid, about 4 by 4, so each future square gets one. Return to the oven.

Tip: Adding them at the halfway point is the whole trick: from the start, the caramel sinks and welds to the pan base.

Bake for a further 10 to 14 minutes, until the top is matte and a skewer inserted between the candies comes out with thick moist crumbs.

Cool completely in the pan, at least 2 hours, then lift out by the parchment and cut into 16 squares, wiping the knife between cuts.