Jerusalem Artichoke and Sage Gratin

Peel Jerusalem artichokes and cut into 1-inch pieces. In a stainless-steel or enameled saucepan combine artichokes, milk, and enough water to cover artichokes by 1 inch and simmer until tender, about 30 minutes. (Milk will help prevent artichokes from discoloring.) While artichokes are cooking, in a large skillet heat 2 tablespoons butter over moderately high heat until foam subsides and sauté onion, garlic, and 1 tablespoon sage until onion is golden, about minutes.

Preheat oven to 425° F.

Drain artichokes and in a food processor pulse with onion mixture and Parmesan until smooth. Spoon purée into a 2-quart buttered gratin dish. In large skillet melt remaining 3 tablespoons butter over moderate heat and sauté bread crumbs with remaining 2 tablespoons sage until golden, about 5 minutes. Season bread crumbs with salt and pepper and sprinkle evenly over purée. Gratin may be prepared up to this point 2 days ahead and chilled covered.

Bake gratin in middle of oven until hot and bread crumbs are a shade darker, about 20 minutes, and garnish with fried sage leaves.

To make fried sage leaves:

In a small skillet heat 1/8 inch oil over moderately high heat until hot but not smoking and fry sage leaves, 1 at a time, about 3 seconds, until crisp, transferring with a slotted spoon to paper towels to drain. Sprinkle sage leaves with coarse salt.