Chocolate chip and nut shortbread

Preheat the oven to 160°C.

Put the butter, flour, sugar, vanilla and egg in a food processor and process until the mixture comes together, about 5 minutes.

On a lightly-floured work surface, turn the dough out and add the chocolate and walnuts and knead gently until well combined.

Line a 23 x 30cm baking tray with baking paper and press the chocolate mixture to evenly line the tray. With the back of a spoon smooth over and score the top into long bars. Prick with a fork and bake until the top is lightly golden, about 40 minutes. Slice and serve.