Sift the flour and baking powder and set aside.

In the bowl of a stand mixer fitted with a paddle attachment, beat the butter until pale, about 3 minutes. Add the sugar gradually and continue to beat. Add the eggs one at a time and the vanilla extract. 

Add the flour & baking powder and briefly mix then add the raisins and again, briefly mix. You should a have a sticky dough.

Sprinkle a table surface lightly with flour and scrape the dough out the bowl. Briefly knead to form a ball and then shape into a log about 25cm in length. If you like quite small pieces, roll it a bit longer to 30 cm. Place it on a baking sheet lined with baking paper or a silicone mat and flatten it slightly. Bake for 30 minutes until golden brown. Remove and turn the oven down to 150C.

Allow the biscotti log to cool enough to handle then remove it from the baking paper or silicone. Slice into pieces as thin as you like. Pace these black on the lined baking sheet and bake at 150C for 15 – 20 minutes. Turn the oven off and leave to dry out further for about 30 – 60 minutes. 

Once cool, melt the chocolate in the microwave or in a double boiled and dip each piece of biscotti in the chocolate. Drizzle any remaining chocolate in a zig zag across the other half of the biscotti to create a lacey look.