Brown the Butter: In a light-coloured saucepan, melt the 225g unsalted butter over medium heat. It will bubble and foam. Continue cooking, stirring occasionally, until golden brown flecks appear at the bottom of the pan and a deep, nutty aroma fills your kitchen. This process usually takes about 5-8 minutes. Pour the browned butter, including the browned bits, into a heatproof bowl and let it cool for about 10-15 minutes until it's just warm, not hot.

Cream Sugars and Butter: In a large mixing bowl, combine the cooled brown butter with the 150g light brown sugar and 100g caster sugar. Beat with an electric mixer on medium speed for 2-3 minutes until the mixture is light, fluffy, and a pale caramel colour. The sugars should be well incorporated, creating a creamy texture.

Add Eggs and Vanilla: Crack in the 2 large eggs, one at a time, beating well after each addition until fully incorporated. Add the 1 teaspoon vanilla extract and beat for another minute until the mixture looks smooth and glossy, with a lovely pale yellow hue.

Combine Dry Ingredients: In a separate medium bowl, whisk together the 270g plain flour, 1 teaspoon bicarbonate of soda, and ½ teaspoon fine sea salt until thoroughly combined. The mixture should appear uniform with no lumps.

Mix Wet and Dry: 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 streaks of flour are visible and the dough forms a soft, pliable ball. Gently fold in the 150g milk chocolate chips and 100g dark chocolate chips until evenly distributed throughout the dough, which will have a rich, deep golden-brown colour.

Chill the Dough: Cover the bowl with cling film and refrigerate the dough for at least 30 minutes. This chilling time is crucial for the texture and helps the flavours meld beautifully. When you press it gently, the dough will feel firmer and less sticky.

Preheat and Scoop: Preheat your oven to 180°C (160°C fan/Gas Mark 4). Line a baking tray with parchment paper. Scoop rounded tablespoons of dough onto the prepared tray, leaving about 5cm between each cookie to allow for spreading. I often use an ice cream scoop for consistent sizing.

Bake the Cookies: Bake for 10-12 minutes, or until the edges are golden brown and set, but the centres still look slightly soft and puffed. When you remove them, they’ll smell heavenly, with a deep, buttery chocolate aroma. For an extra touch, sprinkle a tiny pinch of flaky sea salt on top immediately after they come out of the oven.

Cool and Enjoy: Let the cookies cool on the baking tray for 5 minutes before transferring them to a wire cooling rack to cool completely. This allows them to set properly, ensuring that delightful chewy texture.