Scottish Shortbread

Make the dough

1. In the bowl of a stand mixer fitted with the paddle, cream together the butter and icing sugar on medium speed until smooth and paler, 2 to 3 minutes. Scrape the bottom of the bowl with a rubber spatula to make sure the butter is fully incorporated with the sugar.
2. Add the cornstarch and any flavour additions and beat until combined, 1 minute.
3. In a medium bowl, whisk together the red spring wheat flour, sifted all-purpose flour, and salt. Add half of the dry ingredients to the wet ingredients and stir on low speed for 30 seconds. Add the remaining dry ingredients and stir just until a smooth paste forms. Avoid over- mixing, which will develop the gluten in the flour and result in tough shortbread.

Shape the dough and chill

1. Place the cookie dough in the centre of a piece of parchment paper or plastic wrap. Fold one end of the parchment towards you over the dough. Holding a bench knife nearly parallel to the work surface and angled slightly downward, push towards the dough, forcing it into a log in the parchment. The log should be 3 inches (8cm) in diameter.
2. Place the log in the fridge for at least 8 hours or up to 5 days. If there is space in the fridge, it is best to hang the log to prevent any flat sides. I find this is more achievable if the log is wrapped in plastic rather than parchment paper. Otherwise, roll a kitchen towel around the wrapped log to provide some padding, then lay the log on a shelf.

Bake the cookies

1. About 45 minutes before you plan to bake the cookies, arrange the oven racks in the upper and lower thirds of the oven and preheat to 175°C/350°F/Gas Mark 4.
2. Line 2 large baking sheets with parchment paper or silicone baking mats.
3. Remove the shortbread log from the fridge and unwrap it. Cut the log crosswise on a cutting board into slices about ½ inch (1cm) thick. Arrange the cookies on the lined baking sheets, leaving 2 inches (5cm) between them to allow for even baking. (Typically, these cookies don’t spread.)
4. Bake the cookies until lightly golden brown on top, 10 to 12 minutes. If you are not using a convection oven, you may need to rotate the cookies halfway through. If they have spread a little, while they are still hot, use a cookie cutter to trim the edges. This step isn’t necessary but will make the biscuits uniform and tidy.
5. Allow the shortbread to cool on the baking sheet for 1 hour.
6. Store the shortbread in an airtight container in a cool, dry place for up to 3 days.