Whisk the oil, lime juice and some seasoning together in a shallow dish. Add the chicken breasts, turn to coat, then leave to marinate for 15-30 minutes.
Meanwhile, preheat the oven to 400°F Roast the tomatoes in a non-stick roasting tin for 4-5 minutes, until the skins just burst. Remove from the oven and cut into small sprigs. Set aside.
Drop the peas into a pan of salted boiling water, bring back to the boil, then drain. Refresh under cold water and drain well. Set aside.
Scatter the lettuce, arugula, mint and scallions over 4 plates.
Heat a non-stick griddle or frying pan over a high heat until smoking hot, then reduce the heat to medium. Cook the chicken for 6-8 minutes each side, until cooked through. Slice and place on the salad.
Halve, stone and peel the avocado, then slice over the salad. Add the tomatoes and scatter with the peas.
Whisk the dressing ingredients together, season and spoon over the salad. Serve immediately.