Mix the ginger with the soy and plum sauces, oil and honey in a deep dish, then add the duck legs, turning to coat. Cover and chill for at least 20 mins.
Heat oven to 160C/fan 140C/gas 3. Lift the duck legs onto a non-stick baking tray, then roast for 1½ hrs until crisp and golden. Meanwhile, tip the remaining marinade into a small saucepan and simmer for 2 mins, then cool. When the duck is cool enough to handle, remove the skin and shred the meat. Mix with the cooled marinade and spring onions.
Unroll the pastry onto a floured surface and roll it out even thinner until you have a sheet large enough to stamp out 10 circles using a 9-10cm round cutter. Put 2 tsp of the duck filling in the middle of each circle, brush the edges of pastry with a little egg, then fold the pastry circles in half, pressing to seal so you have a half-moon shape (any remaining duck makes a great filling for wraps). Transfer the puffs to a baking sheet and brush with more egg. Can be frozen for up to 1 month. Bake for 15-20 mins until golden, or 5 mins longer from frozen.