Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, line a large baking tray with baking paper
For the biscotti dough stir the plain flour, caster sugar, cocoa powder, baking powder and salt together in a mixing bowl
Then stir in the mixed peel and orange zest
Add the eggs and milk, and stir to make a sticky dough
Tip the dough onto the baking tray and shape it into a rectangle, approximately 35cm long and 10cm wide
Bake the dough for 35 minutes. Then leave it to cool on the tray for about 30 minutes
Using a serrated knife, trim off the ends, then carefully slice the cooked dough into about 1" slices and place them onto lined baking trays
Bake the slices again for 30 minutes, turning them over halfway through. They are done when you press the middle and there is no give and they feel dry
Melt the Terry's chocolate orange, you can do this in a microwave safe bowl. Microwave the chocolate for 30 seconds, stir, then microwave in 10 second intervals and stir in between until fully melted
Dip in one of the edges of each biscotti. Add orange sprinkles if you like. Leave to set on some baking paper
Store the biscotti in an airtight container and eat within 2 weeks