Cream Butter and Sugar: In a large mixing bowl, using an electric hand mixer or a stand mixer with the paddle attachment, beat the softened butter and caster sugar together on medium speed for about 3-4 minutes. You’re looking for the mixture to become pale, light, and fluffy.

Add Wet Ingredients: Add the egg yolk, vanilla extract, lemon zest, and 1 tablespoon of lemon juice to the bowl. Beat again for another minute until everything is well combined and smooth. Scrape down the sides of the bowl to ensure it's all incorporated.

Combine Dry Ingredients: In a separate bowl, whisk together the plain flour, cornflour, and salt. This helps to distribute the salt and cornflour evenly.

Form the Dough: Add the dry ingredients to the wet mixture in two batches, mixing on a low speed until just combined. Be careful not to overmix here; stop as soon as you no longer see streaks of flour. The dough will be soft.

Chill the Dough: Tip the dough out onto a piece of cling film. Form it into a flat disc about 2cm thick, wrap it tightly, and place it in the refrigerator to chill for at least 30 minutes. What works best for me is chilling it for a full hour if I have the time, as it makes the dough much easier to handle.

Preheat and Prepare: Towards the end of the chilling time, preheat your oven to 180°C (160°C Fan / Gas Mark 4). Line two large baking trays with baking parchment.

Roll and Cut: Lightly flour your work surface and rolling pin. Unwrap the chilled dough and roll it out to a thickness of about 5mm (the thickness of a £1 coin). Use a 6cm round cutter to cut out your cookies, placing them on the prepared baking trays. Leave a little space between them as they will spread slightly.

Bake the Cookies: Bake for 12-15 minutes, or until the edges are just starting to turn a very pale golden-brown. The centres should still look quite pale. They will firm up as they cool.

Cool Down: Let the cookies cool on the baking trays for 5 minutes before carefully transferring them to a wire rack to cool completely.