4 Tbs. (1/2 stick) unsalted butter
6 large yellow onions, thinly sliced
6 Tbs. chopped fresh basil
5 cups water, vegetable broth or chicken broth
Salt and freshly ground pepper, to taste
4 thick slices coarse country bread, preferably day-old, cut into 1-inch cubes
1/2 cup grated Parmesan or shredded fontina cheese
In a large saute pan over low heat, melt the butter. Add the onions and saute very slowly, stirring often, until caramelized, about 45 minutes. The onions must be sweet and golden but not brown.
Stir in 2 Tbs. of the basil and cook for 5 minutes to flavor the onions.
Add the water, cover and simmer until the onions are quite tender, about 30 minutes more.
Meanwhile, preheat an oven to 350F.
When the onion mixture is ready, season with salt and pepper and remove from the heat.
Place individual ovenproof bowls on 1 or 2 baking sheets and evenly divide the bread cubes among them. Top with the hot onion mixture and then the cheese.
Bake until the cheese melts and the soup is piping hot, 10 to 20 minutes. Garnish with the remaining basil and serve.