Warm ½ tbsp oil in a pan over a medium heat. Fry the chicken over a medium heat for 10 mins, turning once or twice, till golden brown and cooked through.
While the chicken cooks, peel and finely slice the onion. Halve the pepper. Scoop out the seeds and white bits and finely slice. Peel and crush the garlic. Finely chop the chilli, flicking out the seeds for less heat. Finely chop the coriander stalks.
Lift the chicken out the pan and pop on a plate. Add the onion and pepper to the pan with a splash of water. Season. Fry for 5 mins, stirring now and then, till soft.
Stir in the garlic, chilli and coriander stalks to the pan with a pinch of the cayenne (it’s spicy, so use as much or as little as you like). Add the chopped tomatoes. Fill the can with water and add that too. Bring the pan to the boil.
Use two forks to shred the chicken. Add the chicken back to the pan once the soup is boiling. Cover and turn down the heat. Simmer for 10 mins.
Heat your grill to high. Slice 2 of the tortillas into little triangles (you can freeze the remaining tortillas for up to 3 months). Spread out on a baking tray. Grill the tortillas for 8-10 mins, till golden and crisp, turning once or twice.
Taste the soup and adjust the seasoning. Ladle into warm bowls. Top with a few of the grilled nachos, some soured cream and the coriander leaves. Serve with extra nachos on the side.