Put the whole spaghetti squash in a large saucepan with water and bring to the boil. Cover and simmer the squash for 40 minutes.
Place the chicken breast in a steamer for 20 minutes until cooked through. cover in foil to keep warm.
Mix together the basil, garlic, olive oil, lemon juice, pine nuts and salt in a food processor just enough to retain texture. Stir through the parmesan.
When the squash is cool enough to handle, cut in half and scoop out the seeds. Use a fork to shred the chicken. Stir the pesto in with the chicken and vegie spaghetti and serve with a mixed green salad.