Preheat oven to 200degC (390 Fahrenheit). Line two oven trays with baking paper.
Cut any larger baby potatoes in half so they are all roughly the same size. Toss potatoes, carrots, garam masala, curry powder and oil in first prepared tray, season with salt and pepper and bake for about 30 minutes until golden and cooked through.
Combine chicken, tandoori paste, yoghurt, olive oil and salt in a shallow dish or bowl and set aside to marinate for 5-10 minutes. Alternatively marinate overnight.
When potatoes have been roasting for 10 minutes, place chicken thighs flat onto second prepared tray (with sides/lip) and roast until cooked through, about 20 minutes. Rest for 5 minutes before slicing thickly.
While the potatoes and chicken are cooking prepare the salad; roughly chop lettuce; cut cherry tomatoes in half; halve cucumber lengthways and slice thinly on an angle. Arrange all on a platter or toss together in a large bowl.
In a small bowl, mix all curry yoghurt dressing ingredients together well.
To serve, pile salad onto plates with a few roasted potatoes and carrots. Top with tandoori chicken slices, drizzle over curry yoghurt dressing and garnish with coriander leaves.