Bring a large pot of salted water to a boil. Cook tagliatelle according to package instructions, about 8-10 minutes, until al dente. Reserve 1 cup of pasta water, drain pasta, set aside.

In a large skillet over medium heat, add olive oil. Sauté diced onion and sliced mushrooms for 5 minutes, until softened.

Add minced garlic and sauté for 1 minute until fragrant.

Pour in white wine, deglaze skillet, and simmer for 3-4 minutes until wine evaporates.

Reduce heat to low, add heavy cream and cream cheese. Simmer for about 5 minutes until thickened.

Add drained tagliatelle to skillet, toss to coat with sauce. Mix in half of the grated Parmesan cheese. Adjust sauce consistency with reserved pasta water.

Season with salt and black pepper. Serve topped with remaining Parmesan and parsley.