Asparagus Gratin

2 lb asparagus, trimmed and cut diagonally into 1 1/2-inch pieces
2 tablespoons olive oil
2 tablespoons unsalted butter, cut into bits
1/2 cup finely chopped shallots (about 2 large)
1/2 loaf french baguette, cubed
1/4 cup pine nuts (1 1/4 oz)
1/4 teaspoon black pepper
2 oz finely grated Parmigiano-Reggiano (1 cup)
1/2 teaspoon salt
1/2 cup mascarpone cheese
Butter a 2- to 2 1/2-quart shallow ceramic flameproof baking dish.

Cook asparagus in a 5- to 6-quart pot of boiling salted water , uncovered, until crisp-tender, about 4 minutes. Drain in a colander, then transfer to baking dish and keep warm, tightly covered with foil.

Meanwhile, heat oil and butter in a 12-inch heavy skillet over high heat until foam subsides, then cook shallots, stirring occasionally, until pale golden, about 3 minutes. Add bread and pine nuts and cook, stirring, until browned in spots, about 5 minutes. Transfer to a bowl and add pepper, 1/2 cup Parmigiano-Reggiano, and 1/4 teaspoon salt, tossing to combine.

Preheat broiler.

Toss warm asparagus with mascarpone, remaining 1/2 cup Parmigiano-Reggiano, and remaining 1/4 teaspoon salt until combined well.

Sprinkle bread-crumb mixture evenly over asparagus. Broil 5 to 7 inches from heat until topping is golden brown, 1 to 2 minutes.