Mix with your fingertips incorporating the butter, forming a crumbly consistency.
Gather the dough to form a ball.
Press dough into prepared pan
Line a round 8 inch / 20cm cake pan (with removable base) with parchment paper (See notes on baking pans alternatives)
Press out the dough into the pan. Smooth and level the dough with the back of a spoon.
Decorate and pre-slice and refrigerate
Decorate edges with either a fork OR
Roll a fluted cookie cutter around the edge to form a uniform border.
Pre slice into wedges (without cutting all the way through), and use a skewer or fork to poke holes in the shortbread.
Refrigerate for 1 hour before baking.
First bake
Position a shelf in the middle of the oven. Preheat the oven to 320°F/160°C (140° fan)
Sprinkle about 1 Tablespoon of castor or white granulated sugar over the shortbread.
Bake for 35 minutes
Remove from the oven, but don't turn off the oven
Allow the shortbread to cool for 5 minutes. Remove from the baking pan and cut through the pre-sliced lines.
Second bake
Place the shortbread slices onto a baking sheet lined with parchment paper.(I prefer to place them onto the baking sheet with the cut side up. You can place them either way, flat or cut side up)
Return the sliced shortbread to the oven, and bake them for 10 - 15 minutes,until they feel dry and crisp. Turn off the oven, but leave the shortbread inside for 10 minutes.
Remove the shortbread from the oven and set to cool on a cooling rack. They'll continue to crisp as they cool.
Storing
At room temperature: in an airtight container for up to 2 weeks.
To freeze: Baked shortbread can be frozen in an airtight container for up to 3 months.
Notes
Baking pan alternatives:
A springform pan will also work well for this recipe
Any 8 inch / 20cm pan lined with parchment paper that hangs over the sides (this helps when it comes to removing the baked shortbread from the pan).
You can use an 8 inch / 20cm round pan and slice your shortbread into wedges. Or a 20cm square pan and slice your shortbread into fingers.
You can also shape the dough into a ball, roll it out into an 8 inch / 20cm round, and at least ¾ inch/ 2cm thick. Pre cut into wedges then prick with a fork. Refrigerate, then follow the recipe for baking instructions.