- Preheat oven to 180 C / 160 C fan / Gas 4.
- Line two baking trays with baking parchment. Fold a centre pleat in the paper standing up lengthways for one tray, this is to stop the biscotti spreading.
- Add flour, sugar, and baking powder to a large bowl. Sift in if your sugar is lumpy.
- Beat the eggs in a separate small bowl. Add the beaten egg to the dry mixture about 1/4 at a time, stirring well between. You want a slightly wet dough but not a sloppy one - I've never used all the egg.
- Add lemon zest and spices if using, plus all fruit and nuts and mix well.
- Wet your hands, take half the mixture, and quickly form a long log shape. Lay it in one side of the tray prepared with the pleat. Re-wet your hands and repeat for the rest of the mixture. Re-wet your hands again, and shape each log evenly and thinly on the tray (The mixture will spread out. The pleat is to keep the two logs from joining in the middle).
- Bake 30 to 35 minutes until firm, lightly browned, and a skewer inserted in the middle comes out clean. Remove from the oven, and lift the baking parchment off the tray onto a cooling rack. Cool around 20 minutes, then peel each log off the parchment and move to a chopping surface.
- Slice each log with a sharp serrated knife into 1.5cm to 3cm (1/2 in to 3/4 in) wide slices. Try a slight angle for a traditional biscotti shape. Use the knife slowly and carefully, but don't worry about bits falling off - these are the cook's perks!
- Lay each slice cut-side up on the original tray (pleat flattened out), and on the 2nd prepared tray.
- Return to the oven for around 8 minutes, then turn each slice over, then back again for 10 minutes or slightly more. You want them browned, but not too dark. They won't be ultra-crispy yet so don't wait for that to happen in the oven. Remove from the oven.
- Cool until you can handle them safely. They will keep in an airtight container up to a week.
Almonds are the traditional biscotti nut. But macademia nuts are excellent; they're tasty but also softer, and make slicing the 1st bake much easier. (if you use almonds, don't add them whole unless you have a *really* sharp serrated knife) try a 2/3 mix of nuts with 1/3 of pumpkin seeds for colour.
Don't over-do the spices added - 2 different but complementary ones, 1/2 teaspoon each, is enough e.g. cinnamon, allspice, ginger and nutmeg all work.
Most dried fruits are suitable - dates, raisins/sultanas, cranberries, apricots, cherries, you name it. Use one, or two, or more to your taste.
If your dough is very wet and sloppy, don't worry! Just pour it out onto the baking tray and shape with wet hands / utensils into slim logs. They won't rise as much, but they'll still be delicious.