Blanche the sweet corn in boiling water and then put it on the grill and blacken it a little. Finely dice the onions, garlic and ginger. Chop the chillies and add it to the onions. Add the lemon juice and allow to macerate for 10 min. Dice the tomatoes and add to the salsa base. Grill, skin and deseed the peppers. Cut the peppers into a large dice and add to the salsa. Shuck the corn and add the kernels.