Thinly slice the mushrooms and roughly chop the garlic. Cut the each green bean into 3 pieces.
Heat the groundnut oil in a frying pan over medium heat. When it’s hot, add the mushroom and cover. Turn down the heat and sauté for 5 minutes until the mushrooms have released some liquid. Add the garlic and fry for 30 seconds.
Meanwhile cook the rice noodles in hot water according to the packet instructions. This should take 5 minutes. Drain and keep it in the pan, covered with a lid.
Add the soy sauce, lemon juice, chopped spring onion and the beans to the mushrooms, put the lid on and cook for 3-5 minutes over low heat until the vegetables are tender. Stir in the sesame oil. Taste, add more lemon juice or tamari, if needed. Add the cooked noodles, then gently toss.
Serve with the sesame seeds sprinkled on top.