Add the ginger paste, garlic, cilantro, scallion, shrimp, sugar, soy sauce, ½ teaspoon of sesame oil, black pepper, and finely diced water chestnuts to a food processor and pulse several times to make a chunky paste. Let it sit for 10 minutes to allow the flavors to infuse.
Brush the tops of the bread triangles with the remaining 1 tablespoon of sesame oil, then spread some of the shrimp paste onto each triangle, making sure to cover the whole of the surface.
Carefully brush a little egg white onto the top of the shrimp paste, before sprinkling the toast triangles liberally with sesame seeds.
Heat the frying oil in a large, non-stick frying pan, and then gently place the shrimp toast paste-side up for around 2 minutes, until the base is a lovely golden color. Then, gently flip the toast over and allow the other side to cook for 2-3 minutes, until it is a golden color and the shrimp paste is cooked though.
Serve immediately, with sweet chili sauce or soy sauce.