Rinse and grate the courgettes using a grater. Put them in a colander and leave them aside.
Brown the diced bacon in a pan. Remove from the pan and sauté the spring onion cut into rings in the released fat for a few minutes.
Add the courgettes and cook for about ten minutes, adding salt to taste. Then pour the courgettes and spring onion into a bowl and let them cool completely.
When they are cold, add the grated pecorino, breadcrumbs, diced mozzarella, bacon, and eggs.
Mix thoroughly and pour the mixture into a greased pan.
Cover with melted butter and breadcrumbs and cook the gateau in a static oven at 200 ° for about 25 minutes.
Take it out of the oven and let it rest for a few minutes before serving.