In a mixing bowl, add the egg and sugar and use a hand mixer to beat them well until the mixture triple its volume and has a pale yellow colour.
Sift in the flour, baking powder, add the cranberries, orange zest, orange juice, pistachios chopped roughly and orange essence.
Mix to get a sticky dough.
Line a rectangle baking tray with non-stick paper, and add the dough, shaping it into a large sausage (see photo number 4 in the post).
Bake in the preheated oven at 180 degrees Celsius (350 Fahrenheit) for 20-22 minutes until golden.
Remove the biscotti from the oven, and leave it to cool for 5 minutes.
Use a bread knife to cut across diagonally to get biscuits of 1.5 cm in thickness.
Place them onto the baking tray and bake them for a further 10 minutes.
Turn them over, and bake again for extra 10 minutes.
The biscotti will harden more once they are out of the oven and left to cool completely.