Soak mushrooms in boiling water for 30 minutes. Drain and discard stems. Slice.
Chop turkey hindquarter into chunks, using a cleaver to get through the bone. Pour boiling water over pieces to fatten skin then drain and dry with kitchen paper. Brown turkey, over a medium heat, in just enough oil to cover a heavy-based pan. Cook in batches, wiping pan clean with kitchen paper after each batch and adding more oil as necessary.
To a clean pan add fresh oil and return turkey along with soy sauce, sherry, sugar, mushrooms and peel from 1 orange. Bring to the boil.
Turn heat down to simmer , cover and cook, stirring and skimming scum from surface occasionally, until turkey is tender. Season with salt and pepper, remove from heat and stand covered for 5 minutes. Discard orange peel and serve topped with sauce. Garnish with pared peel from remaining ½ orange, and mint sprigs.
