Preheat the oven to 190C/170C fan/Gas 5 and line a baking tray with greaseproof paper. Using an electric mixer, beat the sugar with the eggs until pale and voluminous.
In a large mixing bowl, combine the flour, baking powder, salt, cardamom, cranberries, white chocolate and almonds.Add the egg and sugar mixture to the dry ingredients and mix well to form a soft dough.
Lightly dust the work surface with a little flour and turn the dough out on it, shaping it into a log approximately 25cm long, 5cm wide and 3cm high. Smooth the top, pushing any almonds or cranberries beneath the surface of the dough so that they do not catch while baking.
Transfer to the lined tray and bake for 25 to 30 minutes until pale golden brown and firm to touch. Remove from the oven and set to one side to cool for at least 30 minutes.
Turn the oven down to 170C/150C fan/gas 3½.
Cut the log into 2cm-thick slices. A serrated knife will help. Arrange the biscotti on the same lined tray in a single layer, cut sides facing up.
Bake for 20 to 25 minutes until crisp all over. Remove from the oven and leave to cool on a wire rack.