Beat the egg, oil, vanilla and sugar with an electric mixer until well combined.
Add the rest of the ingredients and briefly mix briefly until to you have a sticky dough.
Empty the dough onto a floured work surface and knead until its is smooth and no longer sticky (add more flour as needed).
Dived the dough into two and roll each half into a fat roll about 30cm long. Place these, spaced apart on a lined baking tray and then put in the fridge or freezer (this cools the dough down which prevents it from spreading – you could do this over night)
While the dough is chilling, preheat the oven to 180C / 350F
Place the tray in the oven and immediately reduce the temperature to 160C / 325F and bake for 20 – 30 minutes and until the biscotti are lightly golden and firm. Remove and allow to cool slightly. Reduce the oven temperature to 100C / 212F
Cut the biscotti on the diagonal into slices about 1.5cm thick and lay these back on the lined baking sheet next to each other.
Return this to the oven and bake for 15 minutes. Place a cloth in the door to keep it slightly ajar and then bake for a further 15 minutes. Remove the cloth and turn off the oven. Allow the biscotti to dry out in the oven until it is cool.