In a large skillet, heat olive oil over medium heat. Add chopped onion, cooking for about 5 minutes until translucent. Incorporate minced garlic, sautéing for an additional minute until fragrant.

Add sliced mushrooms to the skillet, stirring occasionally as they cook. Allow them to brown for about 8-10 minutes. Season with dried thyme, oregano, salt, and pepper. Add white wine if using and cook for 2-3 minutes.

Stir in halved grape tomatoes, cooking for 2-3 minutes until they soften. Set mixture aside.

In a medium saucepan, melt butter over medium heat. Whisk in flour, cooking for 2-3 minutes. Gradually add warmed milk, whisking until the sauce thickens, about 5-7 minutes. Season with nutmeg, salt, and pepper.

Preheat your oven to 375°F (190°C). Cook lasagna noodles according to package instructions until al dente, about 8-10 minutes. Drain and lay flat.

In a greased baking dish, layer Bechamel sauce, lasagna noodles, half of the mushroom and tomato mix, spinach, and mozzarella. Repeat layers, finishing with noodles topped with remaining Bechamel, mozzarella, and Parmesan.

Cover lasagna with aluminum foil and bake for 25 minutes. Remove foil and bake for an additional 20 minutes until golden.

Let the Mushroom Lasagna rest for about 10 minutes before slicing. Garnish with fresh basil if desired.