2 tablespoons olive oil
1 cup chopped onion
2 cups diced zucchinis (1/4-inch dice)
Salt and freshly ground pepper
8 cups sliced mushrooms (about 500 grams)
¼ cup chopped basil
2 tablespoons oregano
1 bunch Swiss chard, ribs removed
1 cup shelled peas
1/3 cup butter
1/3 cup flour
4 cups milk
2 cups ricotta cheese
6 lasagne sheets
½ cup Parmesan cheese
Heat olive oil in a skillet over medium heat. Add onions and sauté until soft, about 5 minutes. Add zucchini and sauté for another 2 to 3 minutes. Season with salt and pepper. Remove onions and zucchini from pan. Add mushrooms, basil, oregano and salt and pepper and sauté for 5 minutes or until soft. Continue to cook until liquid nearly disappears. Add to zucchini and onions.
Bring a pot of salted water to boil over high heat. Add Swiss chard leaves and cook for 1 minute or until wilted. Remove from heat and drain, pressing to remove any excess liquid. Roughly chop. Add top vegetables along with uncooked peas. Season with salt and pepper. Set aside.
Melt butter in a skillet over medium heat.Add flour and stir together to form a roux. Cook over low heat, whisking, for about 2 minutes or until flour is cooked but not golden.
Add milk in a fast stream, whisking vigorously. Bring to a boil, whisking occasionally until sauce thickens. Reduce heat and simmer, whisking occasionally, for 5 minutes longer. Add salt and pepper.
Remove from heat and whisk in ricotta and nutmeg.
Toassemble lasagne, spread ½ cup white sauce over bottom of a buttered 9 x 13-inch rectangle lasagne pan. Cut pasta sheet to fit baking dish and place over sauce. Generously cover pasta with more white sauce. Cover with a layer of vegetable mixture and another sheet of pasta. Repeat until you reach the top of the baking dish (you should have 4 layers). The last layer will be a pasta sheet, covered with sauce and sprinkled with Parmesan cheese.
Bakelasagne until top is golden brown and sauce is bubbling, about 35 to 45 minutes. Let lasagne to stand for about 20 to 30 minutes before serving.