Bring a large pot of salted water to a boil.
Slice mushrooms evenly and mince garlic finely.
Grate Parmesan and measure all ingredients.
Add tagliatelle to boiling water; cook 2–3 min (fresh) or 7–8 min (dried).
Reserve 1 cup pasta water and drain pasta without rinsing.
Melt butter in skillet over medium heat.
Add mushrooms; cook 5–6 minutes until golden.
Add garlic; sauté 30 seconds until fragrant.
Pour in cream and optional white wine; simmer gently.
Stir in Parmesan gradually until sauce thickens.
Add truffle oil (and optional truffle paste or yolk), then season with salt and pepper.
Adjust thickness with reserved pasta water as needed.
Add pasta to sauce; toss 1–2 minutes until glossy and coated.
Serve topped with parsley, extra Parmesan, and a drizzle of truffle oil.