2 heads garlic
1 tablespoon olive oil
5 tablespoons unsalted butter
1/3 cup all-purpose flour
4 cups 2% milk , warmed
1 1/2 teaspoon ground sage
1 teaspoon salt
1/2 teaspoon nutmeg
1 tablespoon water (approx) (optional)
2 pkg (each 312 g) baby spinach
7 cups shredded mozzarella cheese
2 cups finely grated Parmesan cheese
11 to 14 oven-ready lasagna noodles
3 sweet potatoes (about 900 g), peeled and sliced in 1.8-inch thick rounds
1 batch Oven-Roasted Tomatoes (recipe in Cookbook)
fried sage leaves
Béchamel Sauce: Preheat oven to 375°F. Slice off top third of garlic to expose cloves; discard. Drizzle with oil; wrap in foil. Roast on rimmed baking sheet until tender and golden, about 40 minutes; let cool completely. Squeeze cloves into bowl; mash until smooth.
In large saucepan, melt butter over medium heat; whisk in flour. Cook, whisking constantly, for 1 minute. Whisk in milk, sage, salt and nutmeg. Increase heat to medium-high; bring to boil, whisking constantly. Reduce heat to medium; simmer, whisking often, until slightly thickened, 8 to 10 minutes. Remove from heat; whisk in garlic. Let cool slightly, whisking occasionally. Béchamel Sauce will thicken as it cools; thin with water, 1 tbsp at a time, if needed.
Meanwhile, in large dry saucepan, cook spinach over medium-high heat, working in batches and stirring constantly, until wilted, 5 to 7 minutes. (Pan will seem full at first, but spinach will cook down.) Strain; when cool enough to handle, squeeze out excess liquid. Set aside. In large bowl, combine mozzarella and Parmesan. Set aside.
Assembly: In bottom of greased 13- x 9-inch deep baking dish, spread 1 cup of the Béchamel Sauce; arrange 3 to 4 noodles over top, overlapping slightly if needed, and pressing down. Arrange half of the sweet potatoes over top and sprinkle with 2 cups of the mozzarella mixture; top with three-quarters of the spinach. Arrange Oven-Roasted Tomatoes over top. Top with 4 to 5 noodles, breaking to fit, if needed; spread 1 cup of the Béchamel Sauce over top. Top with 2 cups of the mozzarella mixture, remaining sweet potatoes and remaining spinach. Top with 2 cups of the mozzarella mixture and 4 to 5 noodles, pressing down firmly. Spread remaining Béchamel Sauce over top; sprinkle with remaining mozzarella mixture.
Place dish on rimmed baking sheet; cover with greased foil. Bake for 1 3/4 hours. Uncover and continue to bake until cheese is golden, about 15 minutes. Sprinkle with sage leaves; let stand for 20 to 30 minutes before serving.