1. Preheat the oven to 160°C and grease a large baking sheet well.
2. Combine the vanilla extract and coffee granules and stir to dissolve the coffee.
3. Whisk the egg and egg white together in a large mixing bowl.
4. Add the butter, oil, sugar and the reserved coffee mixture and mix well.
5. Stir in the nuts and coffee beans. Sift the flour, baking powder and salt over the mixture and mix well. Divide the dough in two.
6. Shape each half into two logs and wrap in cling wrap. Chill for 30 minutes to firm up.
7. Place the rolls on the baking sheet, allowing room for spreading.
8. Bake for 20 to 25 minutes until golden and firm. Remove from the oven and slice each roll into thin slices. Arrange the biscotti in a single layer on baking sheets, reduce the oven temperature to 80 °C and bake for 20 to 25 minutes.
9. Turn off the oven and allow the biscuits to dry out in the warm oven.
10. Cool completely before storing.
Ginger and almond biscotti: Replace the macadamia nuts and coffee beans with 1 c flaked almonds. Add 1 teaspoon (5 ml) each ground ginger, ground nutmeg, ground cinnamon and 2.5 ml mixed spice to the dry ingredients.
Pistachio biscotti: Omit the coffee granules and replace the macadamia nuts and coffee beans with 1 cup pistachio nuts, roughly chopped.