1 cup whole milk
1/2 cup heavy cream
1 cup grated Parmigiano-Reggiano
2 large eggs
1 cup coarse fresh bread crumbs
1 tablespoon extra-virgin olive oil
Cut broccoli florets into 1-inch pieces, then peel large stems with a knife and cut into 1/2-inch-thick rounds. Cook broccoli in boiling salted water (2 tablespoon salt for 6 qt water) 5 minutes, then drain.
Meanwhile, whisk together milk, cream, cheese, eggs, and 1/2 teaspoon each of salt and pepper.
Put broccoli in a 2-quart shallow flameproof baking dish, then pour milk mixture over top. Toss bread crumbs with oil and a pinch each of salt and pepper, then sprinkle evenly over gratin.
Bake until custard is set, about 30 minutes. Turn on broiler, then broil until bread crumbs are golden brown, 2 to 3 minutes. Let stand 5 minutes and serve.