Cook the Pasta: Bring a large pot of salted water to a boil, then add the spaghetti. Cook according to package instructions until al dente, usually 8-10 minutes. Drain, reserving a cup of the cooking water, and set aside.

Toast the Breadcrumbs: In a large skillet, heat 2 tablespoons of extra-virgin olive oil over medium heat. Add the fresh breadcrumbs and toast them, stirring often, until golden brown, about 3-5 minutes. Season with salt and pepper before removing from heat.

Brown the Butter: In the same skillet, add 4 tablespoons of unsalted butter over low heat. Allow it to melt, watching closely until it turns golden brown and develops a nutty aroma, about 5 minutes.

Sauté the Garlic: Add the minced garlic to the browned butter. Sauté for about 1 minute until fragrant and translucent.

Cook the Mushrooms: Add sliced cremini mushrooms and thyme to the skillet, stirring well. Cook for about 3-5 minutes until tender and nicely browned.

Combine Pasta and Sauce: Add the drained spaghetti to the mushroom-butter mixture, tossing gently to soak up flavors. If dry, add a splash of reserved pasta water.

Add Toasted Breadcrumbs: Sprinkle the toasted breadcrumbs over the pasta and toss to combine. Reserve some for garnishing.

Serve and Garnish: Plate the pasta, garnishing with chopped parsley and drizzle with olive oil as desired. Serve immediately.