Lemon & White Chocolate Biscotti

Another recipe from One Smart Cookie. I've still got brownies left from last week (although very few), and biscuits from the week before, so I thought I'd better make something that will last for a while. Having baked dark and rich things for the past couple of weeks (chocolaty brownies, treacly biscuits) I also wanted something a bit lighter. I've tried making biscotti in the past, but wasn't too happy with the results. I think these have turned out a bit better.
The book gives a basic biscotti recipe, and suggestions for a number of variations. Having a lemon in the fruit bowl, and a bar of Green & Black's white chocolate in the cupboard, that's the one I went for.
Forgive the mixture of measurements in the recipe; some are from the book, some are my measured additions.

Recipe:
30 grams unsalted butter, softened
3/4 cup caster sugar
2 large eggs
1 teaspoon vanilla extract
2 cups plain flour
2 teaspoons baking powder
1/4 teaspoon salt
Zest of 1 lemon, finely grated
100 grams white chocolate (Green & Black's)

Preheat oven to 350f/175C. Line a baking sheet with non-stick baking parchment.
In a large bowl, beat butter, sugar, eggs and vanilla until smooth.
In a medium bowl, combine the flour, baking powder, salt and lemon zest.
Add a few tablespoons of the flour mixture to the wet ingredients. Stir until combined. Add the chopped chocolate and mix well. Continue adding the flour mixture, a few tablespoons at a time, stirring until just combined. If it seems dry, use your hands to complete the mixing until the dough comes together.
Turn the dough out onto a floured surface. Divide in half. Shape each piece into an 8 inch by 3 inch rectangle.
Place the logs, well spaced on the lined baking sheet. They will spread slightly.
Bake for 20 - 25 minutes until firm and starting to crack on top. Remove from the oven and leave to cool for about 15 minutes.
Reduce the oven temperature to 275F/135C
Trim the ends and cut each log into 1/2 - 3/4 inch slices (12 slices per log) with a sharp serrated knife. Place slices cut side down on the baking sheet.
Return to the oven for 15 minutes, then flip over and bake for another 15 minutes.