Photograph: Jonathan Gregson
Slice the chicken breasts across into 1cm-wide strips. Heat 2 tablespoons of the oil in a large casserole or saucepan over a medium-high heat and briefly colour the chicken on both sides, seasoning it with sea salt. You will need to do this in two batches. Transfer to a bowl as each batch is cooked.
Turn the heat down low, add another tablespoon of oil to the pan and gently cook the shallots and garlic for a few minutes until they soften. Stir in the curry paste and cook for 1 minute, then add the chicken stock, half the coconut milk, the lime leaves and whole chillies. Bring the mixture to the boil over a high heat, then simmer, uncovered, over a low heat for 10 minutes.
Add the chicken to the sauce and simmer for 5 minutes. At the same time cook the noodles – you'll need to do this in two batches. Heat 2 tablespoons of oil in a wok or large nonstick frying pan over a high heat. Add the noodles, breaking them up using your fingers, and stir-fry for 2 minutes or as directed on the pack. Transfer to a bowl and cook the remainder in the same fashion. Stir the remaining tin of coconut milk, the fish sauce and sugar into the curry, and bring back to the boil.
You can prepare the curry to the end of step 2 a few hours ahead.
Pile the chicken to one side of warm soup bowls with a pile of the noodles to the other side, then spoon the green curry broth over the chicken and noodles. Scatter over the basil leaves and serve. Leave the whole chillies and lime leaves in the curry sauce when you serve it – and remove as you are eating.
Get ahead: prepare the recipe to the end of step 2 a few hours ahead.