Thai Scallop Ceviche

12 Scallops
3 Spring Onions, finely chopped
1/2 Red Onion, thinly sliced
2 Stalks Lemon Grass
12 Cherry Tomatoes, halved
2 Red Chillis, finely chopped
Handful of basil, chopped
Handful of Coriander, chopped
Juice of 2 Limes
Fish Sauce (same quantity as lime juice)
4 Tsps Sugar

Clean the scallops, removing the coral. Slice each one across the grain to a thickness of a pound coin. Mix the lime juice and fish sauce and marinade the scallop slices in this mixture for 1 hour. Remove the scallops and stir in the sugar. Peel the outer layers from the lemon grass and remove the hard parts at the base. Slice very finely. Add everything back into the lime juice mixture and stir.