Preheat the oven to 160°C/320°F (140°C fan). Grease and line a 20cm square tin with baking paper.
Place the flour, butter and sugar into the Thermomix bowl. Mix for 12 sec/speed 6. Then knead for 30 sec/dough setting. The mixture will look crumbly, like breadcrumbs, but should hold together when pressed.
Tip the mixture into the prepared tin. Press down firmly and evenly with the back of a spoon until smooth. Bake for 30-35 minutes, or until the edges are just starting to turn golden.
Cool in the tin for 5 minutes, then lightly score into squares or rectangles with a sharp knife. (so the lines are clean). Note: I prick holes in the shortbread after baking for decoration - the dough is too soft to do it beforehand.
Leave to cool completely in the tin (about 1 hour) then cut through along the score lines. Remove from the tin and serve.
Notes
Shortbread Tips
Use fridge-cold butter for a perfect short, tender texture.
Press, don't roll - the mixture will look like breadcrumbs; press it firmly into the tin with a spoon and smooth the top with a glass.
Score while warm for clean, neat edges. Cool in the tin before cutting to prevent crumbling.
StorageStore cooled shortbread in an airtight container, separating layers with baking paper, at room temperature for up to 2 weeks.To freeze, place in an airtight container with baking paper between layers and freeze for up to 3 months. Thaw at room temperature before serving.