Preheat the oven to 200°C.
Peel the langoustines and mix shells with tomato purée, celery, carrot, and onion in a bowl.
Roast the shell mixture on a baking sheet for 30 minutes until golden.
Reduce oven temperature to 170°C.
Pour 500ml olive oil over the shells and roast for 60 minutes.
Strain the oil through a fine sieve, discarding the solids.
Sauté small courgettes and thyme in olive oil until golden and tender.
Boil the pasta in salted water for 2 minutes.
Add courgette ribbons to the pasta water and cook for 1 minute before draining.
Combine the pasta, ribbons, and sautéed courgettes, then season with salt and pepper.
Serve topped with langoustines, parmesan, and a drizzle of the infused oil.