Pick the oregano leaves off their stalks and finely chop them. Zest the lemon. Set a large frying pan over a medium-high heat. Pour 1 tbsp olive oil into the pan and scatter in the breadcrumbs with a good pinch of salt and pepper. Cook for 3-4 mins, stirring frequently, till crisp and golden. Stir in the zest and oregano and scoop into a bowl. This is your pangratto. Set aside.
Fill a large pan with water, add a pinch of salt and bring to the boil.
While the water is heating, peel the onion and garlic and finely chop them. Finely chop the chilli, flicking out the seeds and white pith for less heat. Trim the round courgettes and slice them into thin strips. Pick the mint leaves and roughly chop them.
Add the pasta to the boiling water and cook for 8 mins.
While the pasta is cooking, wipe the large frying pan clean and return to a medium heat. Pour in 1 tbsp oil and add the onions, chilli, garlic and a little salt and pepper. Fry for 3-4 mins, stirring occasionally, tilll softened.
Add the courgettes to the frying pan and continue to cook for 2-3 mins.
While the courgettes cook, pour 1 tbsp olive oil into a large bowl and stir in 1 tbsp balsamic vinegar. Add the watercress and toss the dressing through the leaves.
When the pasta is ready, quickly drain it, keeping some of the water form the pan. Add the spaghetti to the frying pan. Spoon in 2-3 tbsp of the starchy pasta water. Season well and toss continuously till the liquid thickens and clings to the pasta.
Pile the pasta onto plates and spoon over the pangrattato. Serve with wedges of the lemon and the watercress salad.