If that name doesn't get you drooling, I think your belly may be broken. This is a ridiculously delicious, warm and cheesy in-season main dish that would be great for any chilly weeknight meal and also would make an exceptional vegetarian main for Thanksgiving. Sage-infused, creamy béchamel hug layers of lasagna noodles, sauteed spinach, onions and garlic, and rosemary-roasted sweet potatoes and mushrooms. A combination of tangy gruyere and sharp parmesan compliments the vegetables throughout the layers and forms an amazingly gooey and crunchy crust on top. And it's surprisingly not too high in calories and fat - I'm in heaven! —Vegetarianized.com
Put a large pot of salted water on the stove. Cook lasagna noodles al dente, about 5-6 minutes. Drain and to keep from sticking, put strainer of noodles in a bowl of cold water. Drain noodles right before assembling the lasagna.
Meanwhile put 1/2 Tbsp EVOO, mushrooms and sweet potatoes in a large casserole dish. Add 1/2 tsp salt and rosemary and toss. Put in oven for 25 minutes, tossing half-way through cooking. Remove from oven and set aside when done. Leave oven on.
For the béchamel, put flour in a large pot. Turn heat on medium and slowly pour the milk over the flour, constantly whisking to avoid lumps. Add onions, sage, garlic, salt and bay leaf. Bring to a boil, cook 1 minute and then remove from heat. Set aside. Right before assembling the lasagna, strain béchamel through a strainer or sieve over a bowl pressing against solids to get all the sauce through. Discard solids.
For the filling, heat 1/2 Tbsp EVOO in a medium skillet over medium heat. Add onions and garlic and saute for 3 minutes. Add 1/2 tsp salt and spinach. Saute 2 minutes, remove from heat and set aside.
Combine cheeses and set aside.
To assemble, spread 3/4 cup béchamel in the bottom of a 9x13 casserole dish sprayed with cooking spray. Layer 3 noodles on top. Top with 1/2 of the mushroom mixture, 1 1/2 cup béchamel, and 1/3 cup cheeses.
Top with 3 more noodles, spinach mixture, 1 1/2 cups béchamel, and 1/3 cup cheeses. Top with 3 more noodles, remaining mushroom mixture, and 1 1/2 cups béchamel. Top with last 3 noodles and spread remaining béchamel on top.
Bake for 20 minutes, sprinkle with remaining cheeses and cook 10 minutes more. This is likely to boil over the sides so lay a piece of foil or put a pan in the bottom of the oven. Let stand 10 minutes after removing from oven and serve hot.