Bring a large pot of generously salted water to a rolling boil—think seawater salty! This seasons the pasta from the inside out for maximum flavor.

While waiting, heat olive oil and 1 tbsp butter in a large skillet over medium-high heat until shimmering and fragrant.

Toss in your sliced mushrooms in a single layer (don't overcrowd—work in batches if needed). Let them sizzle undisturbed for 4-5 minutes until golden and caramelized on one side—this builds incredible depth!

Flip the mushrooms, add the remaining butter, chopped onion/shallot (if using), and minced garlic. Sauté for another 3-4 minutes until everything is soft, aromatic, and irresistibly garlicky. Season with salt and pepper here—they'll drink it up!

Pour in the white wine and let it bubble vigorously for 2 minutes, scraping up those tasty browned bits from the pan bottom (hello, flavor explosion!).

Reduce heat to medium-low, stir in the heavy cream, and simmer gently for 4-5 minutes until the sauce thickens slightly and coats the back of a spoon—pure luxury in the making.

Meanwhile, add your tagliatelle to the boiling water and cook until just al dente (a minute less than package says—it'll finish in the sauce for perfect tenderness).

Reserve about 1 cup of starchy pasta water, then drain the tagliatelle and add it straight to the creamy mushroom pan.

Toss everything together over low heat, adding splashes of reserved pasta water as needed to create a glossy, silky sauce that clings lovingly to every ribbon. Stir in most of the Parmesan and chopped parsley for that final burst of umami and freshness.

Taste, adjust seasoning with more pepper or a pinch of salt, then plate up immediately—top with extra Parmesan, parsley, and maybe a grind of black pepper. Dive in while it's hot and steamy for the best experience!