Heat the oven to 400 degrees F.

Fill a 4-quart saucepan with water and heat over medium-high heat to a boil. Add the cauliflower and cook for 5 minutes or until tender-crisp. Rinse the cauliflower with cold water and drain well in a colander.

Heat 1/2 tablespoon butter in a 1-quart saucepan over medium heat. Add the bread crumbs and cook and stir until the bread crumbs are golden brown.

Heat the remaining butter in a 3-quart saucepan over medium heat. Add the flour and cook and stir for 1 minute. Stir in the milk, broth, bay leaf and garlic and heat to a boil, stirring constantly. Reduce the heat to low. Cook and stir for 10 minutes or until the mixture is thickened. Season with the black pepper. Remove and discard the bay leaf and garlic. Keep the milk mixture warm.

Spray a 3-quart shallow baking dish with the cooking spray. Place the cauliflower into the baking dish. Season with the black pepper. Pour the the milk mixture over the cauliflower. Sprinkle with the prosciutto. Top with the cheese and bread crumb mixture.

Bake for 30 minutes or until the cauliflower is tender and the cheese is melted. Let stand for 15 minutes before serving.