• Preheat the oven to 350ºF and line a large cookie sheet with parchment paper.

Make the Biscotti Dough:

• In a large mixing bowl add the flour, baking powder, salt, and sugar. Mix until combined then make a well in the center.
• Gradually add the lightly beaten egg a little at a time. Use a rubber spatula to work the egg in to the flour mixture. When all the egg has been added you will have a crumbly dry dough.
• Tip the pistachios, cranberries and orange zest into the mixing bowl. Use a butter knife to work these ingredients into the dough so that they are evenly dispersed.
• Lightly flour a surface and turn the dough out on to it. It will look very crumbly and that is fine. Use your hands to bring the dough together into a square shape, briefly kneading the dough until it looks and feels smooth.
• Cut the square in half so that you have two rectangles. Use your hands to shape the rectangles into two even shapes. They should be roughly 7 inches long by 3½ inches wide and 1 inch deep.

Bake the Biscotti:

• Arrange the dough rectangles on to the cookie sheet you prepared earlier. Bake them in the middle of the preheated oven for 30 minutes then remove them from the oven and leave to cool for 30 minutes.
• Reduce the oven temperature to 325ºF.
• After 30 minutes use a sharp serrated knife to slice the dough on the diagonal about 1 inch in thickness.
• Lay the biscotti cut side up on the cookie sheet then return to the oven for 30 minutes.
• After 30 minutes the biscotti should feel dry to the touch. Remove from the oven and transfer to a wire rack to completely cool.

Add the Chocolate and Pistachios:

• Finely chop the chocolate and place in a heatproof bowl set over a pan of simmering water (in a bain-marie). Make sure the bottom of the bowl is not touching the water. Melt the chocolate then dip the cooled biscotti in it coating one end.
• To decorate, sprinkle the extra pistachios on top of the chocolate while it’s still wet and then leave to set.