Finally slice the celery and chop the spring onions and garlic. Cut the green beans into 3 cm pieces.
Heat the olive oil in a large saucepan and gently cook the celery and the spring onion for 5 minutes. Add the garlic and cook for another minute or so.
Meanwhile, cut the potatoes into 2cm cubes and break the spaghetti into 3 pieces
When the vegetables are soft, add the potatoes, then stir for a few seconds. Add the stock and bring to the boil.
Add the torn spaghetti bits and cook for 5 minutes.
Add the frozen beans and peas and bring to the boil again. Add the chopped green beans and cook for another 3-5 minutes, until the veggies are tender and spaghetti is cooked.
Turn off the heat and stir in the pesto and chopped parsley.
Serve immediately with a squeeze of lemon juice.