Preheat the oven to 175°C/350°F. Line a baking sheet with parchment (baking) paper.

Sift together flour and baking powder. Add the raisins and walnuts and toss to coat with flour.

In a large bowl, beat butter and sugar until soft and fluffy. Continue to beat and slowly add the eggs and the anise. Spoon in the flour mixture and mix to just combine the ingredients.

Spread the dough on to the baking sheet into the shape of an 8x4-inch log. Bake until the top is golden brown, about 35-40 minutes. Remove the tray from the oven and let the log cool completely.

Use a serrated knife to slice the logs crosswise into 1-cm thick biscotti. Store in an airtight container for up to 2 weeks.