1. In a very large skillet, heat 2 tablespoons of the olive oil. Add the white and shiitake mushrooms, season with salt and pepper, cover and cook over moderately high heat for 5 minutes, stirring once. Uncover and cook over high heat, stirring once, until the mushrooms are browned all over, about 3 minutes. Add the sliced garlic, the shallot and rosemary and cook, stirring, until fragrant, about 2 minutes. Add the Marsala and cook until evaporated, about 30 seconds. Add the vinegar and cook, stirring, for 30 seconds. Stir in the minced garlic, olives and the remaining 3 tablespoons of olive oil and season with salt and pepper. Cover and keep warm.
2. In a large pot of boiling salted water, cook the spaghetti until al dente; drain. Return the spaghetti to the pot. Stir in the butter and mushrooms and season with salt and pepper. Stir in 1/3 cup of the Parmesan. Transfer the spaghetti to bowls, sprinkle with the chives and serve, passing more Parmesan at the table.
Notes: Variations: The mushrooms can be folded into an omelet, or served with pan-fried chicken breasts or cheese grits.