Place the chicken mince in a mixer jar. Add the soya chunks, salt, pepper powder, onion, garlic and ginger and grind till well blended. Divide into four equal portions and shape them into round patties with damp hands.
Heat the oil in a non-stick pan and shallow fry the patties on both sides till evenly golden brown. Drain on absorbent paper.
To make the sauce, heat the oil in a non-stick pan, add the ginger and sauté for half a minute. Add the orange juice, brown sugar, salt, dark soy sauce and cook till the mixture reduces slightly. Add the tomato puree, red chilli powder and mix. Simmer till it reduces a little more. Add the cornflour mixed in a little water and cook till the sauce is sufficiently thick.
Slice the buns into two horizontally and lightly toast them. Place a lettuce leaf topped with two tomato slices over one half. Place a chicken burger over it and cover with the other half.
Serve immediately with the sauce.