1. Slice your tuna into thin strips.
2. Combine tuna, prawns, chillies, ginger, lemon juice and half the coriander in a non-metalic bowl. Refrigerate for 30 minutes.
3. Heat a griddle pan until smoking hot. Place your bread in the pan and push down until griddle marks are formed. Remove and set aside.  (Toss the prawns in the hot pan for a couple of minutes if you would prefer to have them a bit more cooked than the lemon juice will “cook” them.)
4. After 30 minutes, remove your prawn and tuna mix. The tuna will have changed colour from the acidity in the lemon juice.
5. To serve, place two slices of bread in the middle of each plate. Lay some tuna and prawns on the bread, spoon over some of the lemon, chilli and ginger. Add some fresh coriander.
6. Use a tablespoon to scoop out avocado flesh. Add as a garnish.