chelsea'srecipes

For béchamel sauce
3 tablespoons unsalted butter
2 1/2 tablespoons all-purpose flour
3 cups whole milk,
clove, smashed
3/4 teaspoon salt
1/8 teaspoon black pepper

For mushroom tomato sauce
2 cups boiling-hot water
1 oz dried porcini mushrooms (1 cup)
1 cup chopped onion (1 medium)
2 tablespoons extra-virgin olive oil
2 (14- to 15-oz) cans diced tomatoes in juice
Pinch of sugar
2 tablespoons chopped fresh basil
1/2 teaspoon salt

For assembling lasagne
12 long ruffle-edged dried lasagne noodles (not no-boil)
5 oz finely grated Parmigiano-Reggiano (1 3/4 cups)

Make béchamel:Heat butter in a 2-quart heavy saucepan over moderately low heat until melted, then add flour and cook roux over low heat, whisking, 3 minutes. Add hot milk in a fast stream, whisking vigorously, and whisk in garlic and salt. Bring to a boil, whisking. Reduce heat and simmer, whisking occasionally, 10 minutes, then remove garlic and add pepper.

Make mushroom tomato sauce:Pour boiling-hot water over porcini in a bowl and let stand until softened, about 20 minutes.Lift out porcini, squeezing excess liquid back into bowl, then rinse to remove any grit. Pour soaking liquid through a sieve lined with a dampened paper towel into another bowl. Chop porcini and add to soaking liquid. Cook onion in oil in a 12-inch heavy skillet over moderate heat, stirring occasionally, until softened, 4 to 5 minutes, then stir in tomatoes with juice, sugar, porcini with soaking liquid, and 1 tablespoon basil. Simmer, stirring frequently, until tomatoes have broken down into a chunky sauce, about 25 minutes. Stir in salt and remaining tablespoon basil.

Assemble and bake lasagne:Cook lasagne noodles in a 6- to 8-quart pot of boiling salted water 8 minutes (noodles will not be cooked through), then drain and transfer to a bowl of cold water. Put oven rack in middle position and preheat oven to 425°F. Spread 1 cup béchamel on bottom of a buttered 13- by 9-inch baking dish, reserving remainder for last layer. Drain 3 lasagne noodles in 1 layer on a kitchen towel and arrange over béchamel in baking dish. Spread pasta in dish evenly with one third of mushroom tomato sauce and sprinkle with 1/3 cup cheese. Repeat layering of pasta, mushroom tomato sauce, and cheese twice, then cover with last 3 lasagne noodles. Spread remaining béchamel on top and sprinkle with remaining 3/4 cup cheese. Bake, uncovered, until lasagne is bubbling and top is browned, 30 to 35 minutes. Let stand at room temperature at least 15 minutes before cutting.

Cooks' notes:• Béchamel and mushroom tomato sauces can be made 2 days ahead and cooled, uncovered, then chilled separately, covered. Bring sauces to room temperature before using.• You can assemble lasagne 1 day ahead and chill, covered. Bring to room temperature before baking.Makes 12 first-course or 8 main course servings.