Heat the oil in a deep frying pan and fry the onions and peppers for a few mins until softened. Stir in the chipotle paste for a minute, followed by the tomatoes. Add up to a tomato can-full of water to cover the chicken and bring to a gentle simmer. Add the chicken breasts and gently simmer, turning the chicken occasionally, for 20 mins until the chicken is cooked through.
Bring a large saucepan of water to the boil with the stock cubes. Add the quinoa and cook for 15 mins until tender, adding the beans for the final min. Drain well and stir in the coriander and lime juice, then check for seasoning before covering to keep warm.
Lift the chicken out onto a board and shred each breast using two forks. Stir back into the tomato sauce with the sugar and season. Serve with the quinoa, scattering the stew with some coriander leaves just before dishing up and eating with a dollop of yogurt on the side.