In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add diced onions and sauté until translucent, about 5 minutes. Stir occasionally.

Add minced garlic and sauté for an additional minute until fragrant.

Incorporate 4 cups of sliced mushrooms. Cook for 8 to 10 minutes, stirring often until browned. Season with dried thyme, oregano, salt, and pepper. Add white wine if desired, simmering until evaporated, about 2-3 minutes.

Fold in 2 cups of halved grape tomatoes and cook for another 2 to 3 minutes. Transfer the mixture to a bowl and let cool.

In a medium saucepan, melt 4 tablespoons of butter. Whisk in 1/3 cup of flour, stirring for 2-3 minutes until golden. Gradually add 2 1/2 cups of warmed milk while whisking to avoid lumps. Cook for 5-7 minutes until thick.

Preheat the oven to 375°F (190°C). Boil water and cook lasagna noodles according to package instructions for 8-10 minutes. Drain and lay flat on a towel.

In a baking dish, spread a thin layer of Bechamel sauce. Layer 3 noodles, half the mushroom mixture, fresh spinach, mozzarella, and Parmesan. Repeat layers, finishing with noodles topped with remaining Bechamel and cheese.

Cover with foil and bake for 25 minutes. Remove foil and bake for an additional 20 minutes until golden and bubbly. Let rest for 10 minutes before serving.

Garnish with fresh basil and serve warm, perhaps alongside a salad or garlic bread.