Cook the green beans in boiling, salted water for 3-4 mins, until just tender. Drain and cool under cold running water. This can be done the day before – just keep the beans covered in the fridge.
When you’re ready to eat, heat the butter in a large frying pan until foaming, add the shallots and cook for 4-5 mins, until soft but not coloured. Throw in the beans and toss to coat. Cook for 1-2 mins until heated through, then season. Serve with the pork.