Preheat the oven to 200°C (400°F), Gas Mark 6. To make the soy dipping sauce, put all the ingredients in a small saucepan over a medium-high heat and bring up to boiling point. Reduce the heat and simmer for 2–3 minutes, pour the sauce into a shallow serving dish and set aside to cool.
Meanwhile, place the tuna in the bowl of a food processor or blender with the sweet soy sauce or ketjap manis, ginger, shallot and egg. Pulse quickly to just combine, then stir in 50 g (2 oz) of the panko or breadcrumbs. Form the mixture into 8 small fishcakes and coat each one well in the remaining breadcrumbs.
Place the fishcakes on a lightly greased, nonstick baking sheet and bake in the oven for 15 minutes, or until crisp and golden, turning once.
Once the fishcakes are cooked, arrange them on serving plates with the soy dipping sauce and sweet chilli dipping sauce served separately.