Active time: 2 hr Start to finish: 4 hr (includes making fresh pasta)

　　

Ingredients

Makes 8 first-course or 4 main-course servings

　　

For sauce

1 1/2 tablespoons unsalted butter

　　1 1/2 tablespoons all-purpose flour

　　2 cups whole milk

　　1/4 teaspoon salt

　　1/4 teaspoon black pepper

　　Pinch of freshly grated nutmeg

　　3/4 oz finely grated Pecorino Romano or Parmigiano-Reggiano (about 1/3 cup)

　　

For cannelloni

3 tablespoons extra-virgin olive oil

　　1 small onion, chopped

　　2 garlic cloves, finely chopped

　　10 oz baby spinach

　　1 3/4 cups ricotta (12 oz fresh or 15 oz supermarket-style)

　　1 large egg, lightly beaten

　　1/2 cup chopped fresh flat-leaf parsley

　　3 oz thinly sliced prosciutto (optional), chopped

　　1/4 teaspoon salt

　　1/4 teaspoon black pepper

　　1 oz finely grated Pecorino Romano or Parmigiano-Reggiano ( 1/2 cup)

　　8 (6- by 4-inch) fresh pasta rectangles or 8 oven-ready (sometimes labeled "no-boil") lasagne noodles

　　

Special Equipment

a 13- by 9- by 2-inch ceramic baking dish or other shallow 3-qt flameproof baking dish (not glass)

　　

Make sauce:

Step 1

Melt butter in a 1 1/2- to 2-quart heavy saucepan over moderately low heat. Whisk in flour and cook roux, whisking, 2 minutes. Add milk in a stream, whisking, and bring to a boil over high heat, whisking constantly (sauce will thicken). Reduce heat and simmer, whisking occasionally, 2 minutes, then whisk in salt, pepper, and nutmeg. Remove from heat and whisk in cheese, then cover pan.

　　

Make cannelloni:

Step 2

Heat oil in a 5- to 6-quart heavy pot over moderately high heat until hot but not smoking, then sauté onion and garlic, stirring occasionally, until lightly browned, about 5 minutes. Add spinach and sauté, stirring, until just wilted, about 3 minutes. Remove from heat and cool completely.

　　

Step 3

Stir together ricotta, egg, parsley, prosciutto (if using), salt, pepper, and 1/3 cup cheese in a bowl, then stir in spinach mixture.

　　

Step 4

Boil pasta 2 pieces at a time in a 6- to 8-quart pot of boiling salted water , stirring to separate, until just tender, about2 minutes for fresh pasta or about 6 minutes for oven-ready noodles. Gently transfer with a slotted spoon to a large bowl of cold water to stop cooking, then remove from bowl, shaking off water, and lay flat on kitchen towels (not terry cloth). Pat dry with paper towels. Trim oven-ready noodles (if using) as closely as possible to 6 1/4- by 5 1/2-inch rectangles.

　　

Step 5

Preheat oven to 425°F.

　　

Step 6

Spread 2/3 cup sauce in buttered baking dish. Spread about 1/3 cup ricotta filling in a line along 1 short side of 1 pasta rectangle, then roll up to enclose filling. Transfer, seam side down, to baking dish. Make 7 more cannelloni in same manner, arranging snugly in 1 layer. Spread 1/2 cup more sauce over cannelloni and sprinkle with remaining cheese. Bake, covered with foil, in middle of oven until sauce is bubbling, about 20 minutes.

　　

Step 7

Turn on broiler.

　　

Step 8

Remove foil and broil cannelloni about 5 inches from heat until lightly browned, 2 to 4 minutes. Let stand 5 minutes before serving. Reheat remaining sauce and serve on the side.

　　Cooks' note:

　　• Cannelloni can be assembled (but not baked) 1 day ahead and chilled, covered with plastic wrap. Let stand at room temperature 15 minutes before baking. Remaining sauce will need to be thinned slightly.