Preheat oven to 350°F. Combine all four ingredients and knead until you get an even consistency (expect hand cramps).

Grease a glass dish with butter, place down a layer of brown paper (I use either brown grocery bags or lunch bags) to line the dish. Line the paper with wax kitchen paper.

Add the dough and spread out (it’s better to make a thin layer, the thicker you make the dough the less likely it will bake enough in the middle). Use a fork and poke holes in rows across the shortbread to help bake the inside (I usually make very tight rows of fork holes in it—more holes gives the inside more time to cook before the dough puffs up and closes them).

Stick in the oven, basically try to bake it until it’s ready. The top usually comes out a deep tan or brown, it might help to use a toothpick to see if it’s still doughy in the middle.