Preheat your oven to 180°C/Fan 160°C/Gas 4. Line the base of a 22cm round or 20cm square cake tin with baking paper and set aside.
Tip the dried mango or apricots (or a mix of both) into a small pan and pour in the orange juice. Pop a lid on the pan and bring to the boil, then turn the heat down and simmer for 10 mins till the dried fruit are soft and pulpy. Take the pan off the heat and use a stick blender to blitz them into a purée, or tip everything into a food processor and blend till smooth.
Add the oats to the fruit purée. Finely chop the crystalised ginger and add it to the oats. Tip in the seeds and add ½ tsp mixed spice. Use a flexible spatula or wooden spoon to stir everything together. Taste and add a little more mixed spice if you think it needs it.
Spoon the oat mixture into the prepared tin and smooth the top down with the spatula or the back of a spoon. Bake for 15-20 mins, till dark golden brown and firm. Let the flapjacks cool in the tin for 2-3 mins, then slice into triangles, squares or bars – you should get 6-12 pieces, depending on how big you’d like your flapjacks. Let the flapjacks cool completely, then transfer to an airtight container. They’ll keep for up to 7 days.