Prepare Your Dry Ingredients: In a medium bowl, whisk together the plain flour, bicarbonate of soda, and salt. This ensures the raising agent and salt are evenly distributed, preventing any salty or soapy bites. Set this aside.

Cream Butter and Sugars: In a large bowl using a stand mixer or an electric hand mixer, beat the softened butter, caster sugar, and light brown sugar together on medium speed for about 3-4 minutes. Scrape down the sides of the bowl occasionally. The mixture should become light, pale, and fluffy.

Add Eggs and Vanilla: Beat in the eggs one at a time, mixing well after each addition until fully incorporated. Then, stir in the vanilla extract. The mixture should be smooth and creamy.

Combine Wet and Dry: Gradually add the flour mixture to the wet ingredients in three parts, mixing on low speed until just combined. What works best for me is to stop mixing as soon as the last streaks of flour disappear. Overmixing at this stage can lead to tough cookies.

Fold in the Good Stuff: Using a spatula, gently fold in the semi-sweet chocolate chips and the optional chopped nuts until they are evenly distributed throughout the dough.

Chill the Dough: This is an important step! Cover the bowl with cling film and refrigerate the cookie dough for at least 30 minutes (or up to 24 hours). This prevents the cookies from spreading too much in the oven.

Preheat and Prepare: When you're ready to bake, preheat your oven to 190°C (170°C fan). Line two large baking trays with parchment paper.

Portion the Cookies: Drop rounded tablespoons of the chilled dough onto the prepared baking trays, leaving about 5cm (2 inches) of space between each one to allow for spreading.

Bake to Perfection: Bake for 9-11 minutes, or until the edges are golden brown and the centres look set. The centres might still look slightly soft, but they will continue to cook on the hot tray.

Cool and Enjoy: Let the cookies cool on the baking tray for 2-3 minutes before transferring them to a wire rack to cool completely. This helps them firm up so they don't break.