Put the noodles in a large bowl and pour over enough boiling water to cover. Leave to stand for 10 minutes or according to instructions on the packet.
Heat the groundnut oil in a large preheated wok or heavy frying pan. Add crushed garlic and sliced shallots to the wok or frying pan, and stir-fry for 1 minute.
Drain the noodles thoroughly. Add the green beans and drained noodles to the wok, and stir-fry for about 5 minutes. Add the cherry tomatoes and mix through well.
Mix together the chilli flakes, peanut butter, coconut milk and tomato purée. Pour the chilli mixture over the noodles, toss well until all the ingredients are thoroughly combined and heat through.
Transfer the satay noodles to warmed serving dishes or bowls, and serve immediately.