Cream Butter and Sugars: In a large bowl or the bowl of a stand mixer fitted with the paddle attachment, beat the softened butter, dark brown soft sugar, and caster sugar together on medium speed for about 3-4 minutes. You're looking for a light, fluffy, and pale mixture.

Add Wet Ingredients: Add the eggs one at a time, beating well after each addition. Scrape down the sides of the bowl, then beat in the vanilla extract until just combined.

Combine Dry Ingredients: In a separate bowl, whisk together the plain flour, bicarbonate of soda, baking powder, and salt.

Mix the Dough: Gradually add the dry ingredients to the wet ingredients, mixing on a low speed until just combined. Be careful not to overmix at this stage. I find that stopping just before it's fully incorporated is best.

Fold in Chocolate: Add the chopped dark chocolate chunks and mix on the lowest speed or by hand with a spatula for a few seconds, just until the chocolate is evenly distributed throughout the dough.

Chill the Dough: This step is key! Cover the bowl with cling film and place it in the refrigerator to chill for at least 30 minutes (or up to 48 hours). This solidifies the butter, preventing the cookies from spreading too much and deepening the flavour.

Prepare for Baking: When you're ready to bake, preheat your oven to 180°C (160°C fan) and line two large baking trays with parchment paper.

Shape and Bake: Roll the chilled dough into balls, about 2 tablespoons each. Place them on the prepared baking trays, leaving ample space between each one as they will spread. I usually fit about 6-8 cookies per tray.

Bake to Perfection: Bake for 12-14 minutes. The edges should be set and golden brown, but the centres will still look slightly soft and underdone. This is the secret to a chewy middle! If you're using it, sprinkle a little flaky sea salt over the cookies as soon as they come out of the oven.

Cool Down: Let the cookies cool on the baking tray for 5 minutes before transferring them to a wire rack to cool completely. They will firm up as they cool.