The perfect chocolate chip cookie is a solved problem, and the solution is: chopped chocolate not chips, brown sugar for chew, a proper rest for the dough, and flaky salt on top. This recipe does all four.
Using a chopped bar rather than chips gives you thin shards and dust that streak through the dough and big melting puddles rather than neat rounds that hold their shape. Resting the dough — even just an hour, ideally overnight — lets the flour hydrate and the flavour deepen, and it's the difference between a good cookie and one people ask you about.
They bake in twelve minutes and are best eaten slightly warm, when the chocolate is still soft. The dough freezes as balls and bakes from frozen with an extra minute or two.
Beat the softened butter with both sugars for 2–3 minutes until noticeably lighter and fluffy. Scrape down the bowl.
Beat in the egg, then the extra yolk, then the vanilla, until smooth and glossy — about 1 minute.
Sift the flour, bicarbonate of soda and fine salt over the bowl. Fold with a spatula until almost combined, with a few floury streaks remaining.
Tip in the chopped chocolate, including the dust and shards, and fold through just until evenly distributed and no dry flour remains.
Cover the bowl and chill for at least 1 hour, or ideally overnight, to hydrate the flour and deepen the flavour.
Heat the oven to 170°C fan / 190°C / gas 5 and line two trays with baking paper. Roll the dough into 16 balls (about 45g each), spacing them well apart. Bake one tray at a time for 10–12 minutes, until the edges are set and golden but the centres still look soft.
As each tray comes out, scatter the cookies with a few flakes of sea salt. Leave on the tray for 5 minutes to firm up, then transfer to a rack. Eat warm, or within 3 days.
Chocolate: A 70% dark bar, roughly chopped, is ideal — keep some chunks large. A mix of dark and milk is good if you prefer it sweeter.
Resting: One hour minimum; 24–72 hours is better. The dough can be portioned into balls and frozen for up to 3 months.
Underbake them: Pull the tray when the centres still look soft and slightly underdone — they firm up as they cool and stay chewy.
Size: This makes 16 medium cookies. For bakery-large, make 10 and add 2–3 minutes to the bake.