Preheat the griller. Place the capsicum pieces, skin-side-up, on the rack. Grill 15 cm from the heat for 10 minutes or until the skin is blackened. When the capsicums are cool enough to handle, peel and cut into 2.5 cm strips.
Top each slice of bread with the cheese and grill for 1 minute or until the cheese is slightly melted and the bread is toasted.
Whisk together the vinegar, oil, mustard and brown sugar in a small bowl. Place the lettuce on 4 plates and arrange the capsicum on top. Drizzle the dressing over the salads and place 3 cheese toasts on each. Garnish with the chervil.