Preheat your oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish with a drizzle of olive oil.

Bring a large pot of salted water to a rolling boil. Cook the penne pasta until it is just al dente (about 2 minutes less than package directions). Drain and set aside.

In a large skillet, heat 2 tablespoons of olive oil over medium-high heat. Add sliced mushrooms in an even layer and cook undisturbed for 3-4 minutes until a deep brown crust forms. Stir and sauté for another 4 minutes.

Reduce heat to medium, stir in minced garlic, and cook for 1 minute until fragrant. Add baby spinach in handfuls, tossing gently until just wilted. Season with salt and pepper, then remove skillet from heat.

In a medium saucepan over medium heat, melt the butter and 1 tablespoon of olive oil together. Whisk in the flour and cook for 1-2 minutes.

Slowly pour in the whole milk and light cream, whisking constantly to ensure no lumps form. Bring to a gentle simmer and stir frequently until thickened. Remove from heat and stir in 1/2 cup of Parmesan, nutmeg, and dried oregano.

Combine the drained penne, sautéed mushroom/spinach mixture, and warm white sauce together in the large skillet, folding gently until the pasta is completely coated.

Transfer the creamy pasta mixture into the prepared baking dish. Scatter the shredded mozzarella and remaining 1/4 cup of Parmesan evenly across the top.

Bake uncovered for 20-25 minutes until the cheese is melted, bubbling, and beautifully golden brown. Garnish immediately with chopped fresh parsley before serving.