Peel the onions and slice thinly, do the same with the shallot, then set it aside. Remove the outer leaves of the leek and slice thinly. Crush the garlic with the blade of a knife.

Pour a glug of olive oil in a large thick bottomed pot, then add the butter. Add the crushed garlic, the thinly sliced shallots and a few leaves of sage, then let it cook on low heat for a few minutes, stirring frequently with a wooden spoon.

Add the onions and the leeks, stir again with the wooden spoon and add a pinch of salt.

Cook slowly on low heat for about 45 minutes.

When the onions are soft and silky add the broth and cook over low heat for about half an hour or until the soup is thick enough for you.

Preheat the oven or grill to maximum. Toast the bread on both sides, then ladle the soup into individual serving bowls and place the bread over each bowl. Sprinkle the bread with plenty of grated pecorino cheese, add a sage leaf and finish with a drizzle of good extra virgin olive oil and some freshly ground black pepper.

But the bowl in the oven under the grill until the cheese is melting and golden, then carefully remove from the oven and serve immediately.