Make the tomato sauce: Heat the olive oil in a saucepan over medium-high heat. Add the onion and cook, stirring occasionally, until soft, about 8 minutes. Add the garlic and red pepper flakes and cook 30 seconds. Add the tomatoes, breaking them up with a wooden spoon, and the basil and cook until thickened, about 10 minutes. Season with salt and pepper. Transfer to a blender and puree until smooth; return to the saucepan and add the parsley, honey, 1/4 teaspoon salt, and pepper to taste.
Make the cauliflower Mornay sauce: Preheat the oven to 350 degrees F. Cut off the cauliflower florets and put in a small roasting pan. Drizzle with the olive oil and season with salt and pepper. Add 1 1/2 cups water to the pan, cover with aluminum foil and bake until very tender, about 1 hour. Remove from the oven.
Melt the butter in a saucepan over medium heat. Whisk in the flour and cook 30 seconds. Whisk in 4 cups milk, increase the heat to medium high and bring to a boil, whisking; cook, whisking, until thick, about 5 minutes. Add the cauliflower, reduce the heat to low and cook 5 more minutes. Remove from the heat and let cool slightly, then puree until smooth. Strain into a clean saucepan and bring to a simmer over low heat. Whisk in the nutmeg, cheese, and salt and pepper to taste and cook 1 minute. Thin with some of the remaining 1 cup milk, if needed.
Make the lasagna: Soak the porcini mushrooms in 1 1/4 cups boiling water, 30 minutes. Meanwhile, bring a large pot of salted water to a boil. Add the lasagna noodles and cook 5 minutes; drain and rinse under cold water. Set aside. Preheat the oven to 375 degrees F.
Combine the ricotta, egg, 1/2 cup parsley, 1 teaspoon thyme and 1/2 cup romano cheese in a bowl and season with salt and pepper.
Heat the olive oil in a saute pan over high heat. Add the garlic and cook 1 minute. Add the assorted mushrooms and cook until soft, about 4 minutes. Add the shallots and cook until golden, about 6 minutes. Drain the porcini mushrooms, reserving the liquid, then coarsely chop and add to the pan; cook 1 minute. Deglaze with the porcini soaking liquid and cook until completely reduced, about 6 minutes. Stir in the remaining 2 teaspoons thyme and 1/4 cup parsley and season with salt and pepper. Remove from the heat.
To assemble the lasagna, ladle some of the tomato sauce into a 10-by-14-inch baking dish. Ladle on some of the cauliflower sauce; top with 4 noodles. Top with some of the ricotta mixture, then some of the mushroom mixture, fontina and some of the remaining romano cheese. Season with salt and pepper. Repeat to make 3 more layers, ending with a layer of noodles, cauliflower sauce and romano. Put the dish on a baking sheet, cover with aluminum foil and bake 30 minutes. Uncover and bake until bubbly, 30 to 40 more minutes. Remove from the oven, sprinkle with parsley and let sit 15 minutes before serving. Serve with the remaining tomato sauce.
Photograph by Johnny Miller
Recipe courtesy Bobby Flay for Food Network Magazine