Preheat the oven to 160°C fan / 180°C conventional / Gas Mark 4.
Cream the softened butter and caster sugar together until smooth and combined.
Add the plain flour and mix until the mixture starts to come together into a dough.
Add the chocolate chips and gently mix them through.
Press the dough evenly into a lined 30 × 22cm baking tray.
Prick the top all over with a fork, then chill in the fridge for 20–30 minutes.
Bake for around 30–40 minutes, until lightly golden around the edges.
While still warm, mark out your portions with a knife, then leave the shortbread to cool completely in the tray before separating into pieces.
