Brown the Butter: In a light-coloured saucepan, melt the 225g unsalted butter over medium heat. Watch it carefully as it melts, then begins to foam. Swirl the pan occasionally. You'll notice the butter solids at the bottom turning a deep golden-brown, and a rich, nutty aroma will fill your kitchen – this is the sign it's ready. Once it reaches an amber hue and smells like toasted nuts, immediately remove it from the heat to prevent burning. Pour the browned butter, including all the glorious browned bits, into a large heatproof bowl. Allow it to cool for about 15-20 minutes until it’s warm but no longer sizzling.

Cream Sugars and Butter: Once the browned butter has cooled slightly, add the 180g light brown sugar and 100g caster sugar to the bowl. Use a stand mixer with the paddle attachment or a hand mixer to beat the sugars into the butter on medium speed for about 2-3 minutes. The mixture should become pale, creamy, and visibly fluffy, almost like a light caramel cloud. This aeration is crucial for the cookie's texture.

Incorporate Eggs and Vanilla: Beat in one large egg at a time, ensuring each egg is fully incorporated before adding the next. The mixture should appear smooth and homogenous, with no streaks of egg yolk remaining. Stir in the 1 teaspoon of vanilla bean paste. The batter will be glossy and smell wonderfully sweet and buttery.

Add Dry Ingredients: In a separate bowl, whisk together the 300g plain flour, 1 teaspoon bicarbonate of soda, and ¾ teaspoon fine sea salt. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix; stop as soon as no dry streaks of flour are visible. The dough will look thick and slightly shaggy.

Fold in Chocolate and Chill: Gently fold in the 250g chocolate chips or chopped chocolate until evenly distributed throughout the dough. The dough will be studded with delightful chocolate chunks. Cover the bowl tightly with cling film and refrigerate for at least 3 hours, or ideally overnight. Chilling allows the flavours to meld and prevents excessive spreading during baking, ensuring a chewier cookie.

Bake the Cookies: Preheat your oven to 190°C (170°C fan/Gas Mark 5). Line a baking tray with parchment paper. Scoop rounded tablespoons of dough onto the prepared tray, leaving about 5cm between each cookie. If you like, sprinkle a tiny pinch of flaky sea salt on top of each dough ball. Bake for 12-15 minutes, or until the edges are golden brown and set, but the centres still look slightly soft and gooey. The aroma of warm chocolate and nutty butter will fill your kitchen. Remove from the oven and let them cool on the tray for 5-10 minutes – they will firm up as they cool – before transferring them to a wire rack to cool completely.