Bring a large pot of salted water to a boil. Cook the spaghetti until just al dente, about 1 to 2 minutes shy of the package instructions. Drain and set aside. Lightly toss with a drizzle of oil to prevent sticking.

In a large pan, melt the butter with olive oil over medium heat. Add the chopped onion and cook until softened, about 5 minutes. Stir in the mushrooms and cook until they release their moisture and begin to brown.

Sprinkle the flour over the vegetables and stir to coat evenly. Cook for 1 to 2 minutes to eliminate the raw flour taste. This forms the base for the creamy sauce.

Gradually whisk in the stock, followed by the milk and cream. Stir constantly to avoid lumps. Add the wine if using, then season with nutmeg, salt, and pepper. Simmer gently until the sauce thickens, about 5 minutes.

Add the shredded turkey to the sauce and stir to coat. Let it warm through for a few minutes. Taste and adjust seasoning if needed. Remove from heat and set aside.

Preheat the oven to 180°C (fan 160°C). In a large mixing bowl, combine the cooked spaghetti with the turkey and sauce mixture. Toss gently to ensure even coating without breaking the pasta.

In a small bowl, mix the breadcrumbs with Parmesan and melted butter. This will form a crisp, golden crust that contrasts beautifully with the creamy filling.

Transfer the pasta mixture into a greased baking dish. Spread it evenly, then sprinkle the breadcrumb topping across the surface. Bake uncovered for 25 to 30 minutes until bubbling and lightly browned.

Let the dish rest for 10 minutes after baking. This allows the sauce to settle and makes serving easier. The texture will firm slightly, making for cleaner slices.

Serve warm, garnished with chopped parsley if desired. A side of green beans or a crisp salad complements the richness. A squeeze of lemon can brighten the flavours if preferred.