1. Preheat the oven to 180°C. Line 2 baking trays with baking paper.
2. Using electric beaters, cream butter and sugar in a bowl until pale and thick. Add the egg and vanilla, and beat to combine. Fold in yoghurt, flour and nut mix. Roll slightly rounded tablespoons of the mixture, flatten and place on trays. Bake in the oven for 12 minutes or until golden. Cool on trays for 5 minutes, then transfer to a rack to cool. Keep in an airtight container for up to 3 days.