Preheat oven to 375°F / 190°C / Gas mark 5.
In a medium bowl, combine flour, baking powder and salt. Set aside.
In the bowl of a stand mixer (or medium bowl), beat butter and sugar until light and fluffy. About 4 minutes.
Add eggs one at a time, incorporating fully before adding another egg.
Add vanilla and beat to combine, then add dry ingredients and mix until just combined.
Mix in pistachios and cranberries until mostly combined, do not overmix. You can press them into the dough when forming the loaves, if needed.
On a parchment lined sheet pan, form two loaves of dough roughly 3 inches (8cm) wide and ¾ inch (2cm) thick.
Bake for 22 – 24 minutes. Remove from oven and cool 15 minutes.
Slice loaves into ½ inch slices and lay the slices on their sides.
Reduce heat to 300°F and bake for an additional 20 minutes (Add an additional 5 - 10 minutes if you want the biscotti EXTRA crunchy).
Move to cooling rack to cool completely before drizzling with melted chocolate.