Preheat the oven to 180 C / 356 F. Butter a 24 x 33 cm / 9 x 13 inch baking dish with a little of the melted butter.
Bring a 5-quart / 4.7 L pot of water seasoned with fine salt to a boil. Add the shredded savoy cabbage and blanch for 5 to 6 minutes until just tender but not limp. Drain well in a colander and press out excess water.
In a 2-quart / 1.9 L saucepan, heat the beef broth with the bay leaf until steaming hot, not boiling. Remove the bay leaf and stir in the nutmeg if using.
Line the bottom of the prepared dish with a layer of the stale country or rye bread, sliced 1.5 cm thick, cutting pieces to fit snugly.
Scatter a third of the blanched cabbage over the bread, then cover with a third of the sliced fontina. Grind black pepper over the layer.
Repeat the layering two more times, bread then cabbage then fontina, finishing with a layer of fontina on top.
Pour the hot broth slowly and evenly over the layers in two or three additions, pausing between pours to let the bread absorb it before adding more. The bread should be soaked through but not swimming in liquid.
Drizzle the remaining melted butter over the top layer of cheese.
Bake for 45 to 50 minutes until the top is golden brown and the broth is mostly absorbed into the layers.
Rest the casserole for 10 minutes before cutting into squares or scooping into bowls. Serve hot.