Scottish shortbread, with a chocolate chip variation

Put the flour, sugar, salt, grated cold butter and rice flour in the stand mixer bowl.

Mix with the paddle on low until pebbly, then on medium 10 to 15 more minutes, scraping down, until the dough clears the bowl and squeezes like play dough.

By hand: work to pebbly, then squeeze and turn four to five hundred times, 15 to 20 minutes.

Press the dough onto a parchment-lined half sheet tray with a smaller tray, then shape into a rough nine by seven inch rectangle and square it with a dough scraper.

Perforate trimming lines and rectangles with a ruler, every two and a half inches top to bottom; score each rectangle six times with a fork.

Bake at 275F / 135C for 45 minutes to an hour, until set with a little golden brown at the edges; longer for crunchier.

Rest 10 minutes on the tray, then cut warm on the perforations with a serrated knife, on the sheet; cool on a wire rack.

Chocolate chip shortbread: replace 55 g of the sugar with brown sugar, add 3 g vanilla, mix about 15 minutes until the dough clears the bowl, then mix in 115 g chopped dark chocolate 25 to 30 seconds; shape and score the same.

Bake the chocolate chip shortbread 45 minutes to an hour at 275F / 135C (about 55 minutes); cool about 10 minutes and cut on the tray.