Spiralize courgettes, salt lightly, and leave in a colander for 15 minutes. Pat dry with kitchen paper.
Heat 1 tbsp oil in a large pan over medium-high heat. Add onion, carrot, and celery — cook 8 minutes until softened. Add garlic and cook 1 more minute.
Increase heat to high. Add turkey mince and break apart aggressively with a wooden spoon. Cook 5–6 minutes until browned with no pink remaining.
Stir in tomato paste and cook 2 minutes. Add crushed tomatoes, stock, oregano, basil, and chilli flakes. Stir well.
Reduce heat to low and simmer partially covered for 20 minutes, stirring occasionally, until sauce is thick and rich.
When ready to serve, heat a dry non-stick pan until very hot. Add zoodles and sauté for 2 minutes maximum. Season and divide into bowls.
Spoon bolognese over the zoodles. Finish with Parmesan if using.