Tear the leaves and any threads from the corn cobs and stand them upright in a wide bowl. Moving around each cob, cut off the kernels into the bowl: don’t shave too close to the cob.
Tear open the chipotles and discard the seeds and stem. (Their heat varies, as does their size, so if you are confident you love heat, use both chillies, or use one to start with, because you can always add the second one at the end.) Finely chop the chilli.
Steam the beans for four minutes, until tender but still with a little crunch. Lift out and then use the steaming water, topped up if needed, to cook the noodles as per the packet instructions, then drain, rinse in cold water, toss with a teaspoon of oil and set aside.
Heat the oil in a wok on a high flame, then stir-fry the onions, corn and chilli for a few minutes. Season generously, add the garlic and peanuts, and stir-fry until the garlic starts to go translucent.
Add the prawns and stir-fry for a few minutes, until they turn pink and look a little caramelised around the edges; the corn should by now have also taken on some colour.
Taste, add more chilli if you want more spice, then add the fish sauce, lime juice, beans and noodles, and toss to heat through. Add more lime or fish sauce to taste, scatter over the mint and serve in deep, warmed bowls.