Preheat the over to gas 6, 200˚C, fan 180˚C. Drizzle the chicken breasts with olive oil. Bake for 20-25 mintues, until cooked through.
Half fill a large saucepan with water and bring to the boil. Add the potatoes and mint sprigs, if using. Cook for 15 minutes until potatoes are tender.
While the potatoes are cooking, heat a little of the oil in large frying pan and cook the bacon for 3-4 minutes until crisp. Drain on kitchen paper.
Return the pan to the heat. Snip each vine of tomatoes in half and cook for 6 minutes over a low heat, turning once, until just soft. Remove and set aside. Put the remaining olive oil and balsamic vinegar into the warm frying pan, and stir until warmed through.
Drain the potatoes and put half in a bowl to let cool. Arrange the lettuce leaves over four plates and divide the potatoes between each. Place the sliced avocado and chicken on top, along with the bacon.
Pop a short vine of warm tomatoes on top of each, scatter over the basil leaves and drizzle with a little warm dressing from the pan. Season with pepper and serve immediately.