Finely chop the garlic cloves.
Using a bean slicer, shred the runner beans into long strings, then cut them in half.
Slice the mushrooms.
Heat the oil a frying pan and add the mushrooms, garlic and thyme leaves. Put a lid on and gently sauté for about 6-8 minutes, until soft. If the mushrooms are not releasing enough liquid, add a splash of water. Add the stock and the runner beans.
Bring to the boil, cover and cook for about 5 minutes, until the beans are tender.
Add the lemon juice. Season with salt and pepper, and sprinkle with the lemon zest and fresh parsley leaves.