Preheat oven to 375°.
Heat oil in a large nonstick skillet over medium-high heat. Add 1 cup onion and garlic, and cook 1 minute, stirring constantly. Stir in the salt, mushrooms, and jalapeños. Arrange chard over mushroom mixture. Cover, reduce heat, and cook for 15 minutes or until tender. Stir in 2 tablespoons parsley.
Combine 1 cup onion, water, and tomatoes in a blender, and process until smooth. Pour the tomato mixture into a saucepan. Bring to a boil; cook 4 minutes or until slightly thick. Arrange 16 tortilla quarters in a single layer in a 13 x 9-inch baking dish. Spread about 1 cup mushroom mixture over the tortilla pieces. Top with 1/2 cup tomato mixture. Sprinkle with 1/3 cup cheese. Repeat layers twice, ending with 1/3 cup cheese. Bake at 375° for 20 minutes or until cheese melts. Top each serving with sour cream and 2 tablespoons parsley.