In a blender blend together the garlic paste, the vinegar, 2 tablespoons of the oil, the water, the cumin, the Tabasco, the bread, half the tomatoes and salt and pepper to taste until the mixture is smooth, transfer the mixture to a bowl, and stir in the remaining tomatoes, the cucumber, the bell pepper, the onion, and the coriander or parsley.
Brush the chicken with the additional oil, season it with salt and pepper, and grill it on a rack set 5 to 15 cm over glowing coals, or in a hot well-seasoned ridged grill pan, covered, over moderately high heat, for 5 minutes on each side, or until it is cooked through. Cut the chicken on the diagonal into 1 cm-thick slices and serve it with the salsa.