This dish is a little unusual - but if you love the broth soaked croutons oozing with cheese in French Onion Soup or a crispy grilled cheese sandwich with a bowl of rich chicken broth alongside, you are going to love this!
Preheat oven to 400 degrees F. Heat the broth to a simmer and keep it hot
Butter the sides and bottom of a baking dish.
Shred the fontina and toss with Parmigiano.
Arrange half of the bread slices in one layer in the baking dish. Ladle out 1 cup of broth, and drizzle over the bread slices. Sprinkle half of the cheese on top of the bread in an even layer.
Cover the cheese with the remaining bread slices.
Moisten these slices with another cup or so of stock; top the bread with all the remaining cheese.
Cover the casserole with foil and bake until heated through, about 25 minutes.
Remove the foil, and continue baking for 10 minutes until the top is golden brown and bubbly.
Let cool for 5 minutes.
Cut into squares and transfer to a shallow soup or pasta bowl.
Ladle hot broth over each portion and serve piping hot with additional grated cheese.