WHAT YOU NEED

70 g (21/2 oz) raw walnuts
170 g (6 oz) dark chocolate (60–70%)
240 g (8½ oz) unsalted butter, cool and pliable
240 g (8½ oz) light muscovado (or soft brown) sugar
100 g (3½ oz) demerara sugar
5 g (⅛ oz/1/2 teaspoon) vanilla paste
50 g (1¾ oz) egg (approx. 1 egg)
20 g (¾ oz) egg yolk (from approx. 1 egg)
220 g (8 oz) plain (all-purpose) flour
2 g (1/16 oz/heaped 1/2 teaspoon) lapsang souchong tea leaves, finely ground in a spice grinder
8 g (¼ oz/1 teaspoon) bicarbonate of soda (baking soda)
2 g (1/16 oz/¼ teaspoon) fine sea salt
cooking oil spray
sea salt flakes, for the salty sprinkle

Preheat the oven to 150°C (300°F). Put the walnuts on a baking tray and toast in the oven for about 20 minutes, or until golden brown all the way through. Turn the oven off. Cool the walnuts quickly in the fridge, then coarsely chop. Chop the chocolate into large gravelly pieces and mix with the nuts. Set aside.

Brown half (120 g/4½ oz) of the butter in a small 20 cm (8 in) wide saucepan (see page 63). Set aside at room temperature.

While the brown butter is cooling, place the remaining butter, both sugars and vanilla in the bowl of an electric stand mixer. Using the paddle attachment, beat on speed 4 (medium) for about 8 minutes. The mix will look more like sugary paste than soft and creamed. This is because the sugar to butter ratio is high, but this will be corrected when the brown butter is added.

Meanwhile, lightly mix the egg and yolk in a small bowl with a spatula. Sift the flour, ground tea, bicarbonate of soda and salt into another bowl and set aside.

Reduce to speed 2 (above low) and slowly stream the brown butter into the bowl. Beat for 3 minutes. Add the egg mix in two batches and beat for 2 minutes on speed 8 (under high). The mix should look pale and creamy but holding a very soft (but not liquid) structure.

If the creamed mix has overheated and is slack and melty, remove the bowl and attachment from the mixer and place in the fridge until it starts to harden around the edge of the bowl. Place back on the machine and continue beating. A melted base makes the cookies overspread, and a little greasy when baked.

Reduce to speed 2 (above low) again, add the chocolate and nuts and mix for 1 minute until only just incorporated. Add the dry ingredients and mix for a final minute. Take the bowl off the mixer and give the dough a thorough and final mix with a stiff spatula.

A final mix with a plastic spatula ensures no butter streaks are left in the dough. Any buttery seams will show in the baked cookie – while still delicious, it will bake a little funny lookin’.

Line a tray with baking paper or plastic wrap. Using a #20 ice-cream scoop, fill a scoopful of dough and level the top. Release the scoop onto the tray. This will give you a compact portion of dough. Place the scoops closely together on the tray. Alternatively, measure the dough as 2 full tablespoons each or weigh to 40 g (1½ oz) and roll into a sphere. Cover and chill overnight.

The next day, preheat the oven to 130°C (265°F). Lightly spray a baking tray with cooking oil spray and line with baking paper. Arrange the dough balls on the tray, spacing them about 3 cm (1¼ in) apart to allow for spreading. Sprinkle a few flakes of sea salt on top of each cookie. Bake for 25–30 minutes until golden brown.* The cookies will still be soft but will firm up when cool. Bake a little more if they are too pale or you prefer a crispier cookie.

Most importantly: optimal wait time before eating is 20 minutes.

* If you get severe overspread, reshape the cookies by stamping with a cookie cutter while they are still warm. If you declare cookie failure, crush them for a cheesecake crumb or serve cookie shards with good vanilla ice cream and chocolate fudge sauce. A kinda DIY chocolate chip cookie sundae.

Keeps Baked – 1 week in an airtight container. They are happily recrisped in a warm oven. Unbaked – the dough keeps for up to 4 days in the fridge, then frozen for up to 3 months.