1.Preheat oven to moderately slow.
2.Beat butter, sugar and extract in small bowl with electric mixer until pale and fluffy. Transfer mixture to large bowl; stir in sifted flours and nuts in two batches. Press ingredients together. Turn onto lightly floured surface; knead until smooth (do not over knead).
3.Divide mixture into two portions. Roll each portion, between two sheets of baking paper, into 23cm circle. Press an upturned 22cm loose-based fluted flan tin into shortbread to cut rounds. Cut each round into 12 wedges. Place on lightly greased oven trays; mark with a fork, sprinkle with extra sugar.
4.Bake in moderately slow oven about 20 minutes or until a pale straw colour. Stand on tray 10 minutes before transferring to wire rack to cool.
Store biscuits in an airtight container for up to three weeks. Suitable to freeze for up to three months.Note