Brown the Butter: Place the cubed butter in a light-coloured saucepan over medium heat. Watch it carefully as it melts, then begins to foam. Continue to cook, stirring occasionally, until the foam subsides, and you start to see tiny brown bits forming at the bottom of the pan. The butter will turn a beautiful amber colour and emit a rich, nutty aroma, reminiscent of toasted hazelnuts. This usually takes about 5-8 minutes. Immediately pour the browned butter, including all the delightful brown bits, into a heatproof bowl to stop the cooking process. Let it cool for about 15-20 minutes until it’s warm but not hot to the touch.

Cream Sugars and Butter: Once the browned butter has cooled slightly, add the light brown sugar and granulated sugar to it in a large mixing bowl. Using an electric mixer, beat on medium speed for 2-3 minutes until the mixture is light in colour and fluffy in texture. It should look pale and aerated, almost like a thick caramel mousse.

Incorporate Eggs and Vanilla: Add the eggs, one at a time, beating well after each addition until fully incorporated. The mixture will become smoother and glossier. Stir in the vanilla extract until its sweet, familiar scent blends with the nutty butter.

Add Dry Ingredients: In a separate bowl, whisk together the plain flour, baking soda, and fine sea salt. Gradually add the dry ingredients to the wet mixture, mixing on low speed until just combined. Be careful not to overmix; stop as soon as you no longer see streaks of flour, maintaining a slightly shaggy, soft dough.

Fold in the Goodies: Gently fold in the milk chocolate chips, dark chocolate chips, and toffee bits using a spatula. Distribute them evenly throughout the dough. The dough will feel substantial and slightly sticky, with visible pockets of chocolate and toffee.

Chill the Dough: Cover the bowl with cling film and chill the dough in the refrigerator for at least 2 hours, or ideally overnight. This resting period is crucial for the flavours to meld and for the cookies to maintain their shape during baking. The dough will firm up considerably and deepen in colour.

Preheat and Prepare: When you're ready to bake, preheat your oven to 180°C (160°C fan/Gas Mark 4). Line two baking trays with parchment paper.

Scoop and Bake: Scoop generous tablespoon-sized portions of dough (about 30-40g each) onto the prepared baking trays, leaving about 5cm between each cookie to allow for spreading. Sprinkle a tiny pinch of flaky sea salt on top of each dough ball if desired. Bake for 10-12 minutes, or until the edges are golden brown and set, but the centres still look slightly soft and gooey. The kitchen will fill with a glorious, buttery, chocolatey aroma.

Cool and Enjoy: Let the cookies cool on the baking trays for 5 minutes before transferring them to a wire rack to cool completely. This allows them to firm up without breaking. Once cooled, they will have a slightly chewy texture and a beautiful golden-brown underside.