Preheat the oven to 200°C/gas mark 6. Place the cashew nuts in a small roasting tray and roast for 5-8 minutes, until lightly browned. Leave to cool.
Place the coconut milk, lemongrass, ginger and stock in a wide pan and bring to a simmer. Lower the heat and add the chicken breasts, adding more water if necessary to ensure the chicken is completely covered. Simmer for 15 minutes until the chicken is cooked through, then transfer to a plate.
Place the mango, avocado, coriander, red pepper, chilli, spring onion and lime juice in a bowl, then season and mix well. Shred the cooked chicken and stir through, then top with the cashew nuts.
If following the Whole 30 diet, please ensure your coconut milk and chicken stock is Whole 30 compliant