Bring a large pot of water to boil and cook gnocchi according to package directions. Reserve 1/2 cup pasta water and set aside.
Add butter to a medium-sized frying pan over medium heat. Once melted, add onion, garlic and salt and pepper. Cook until onion is softened, about 3-4 minutes.
Add the mushrooms and cook down until mushrooms are soft and tender, about 5-6 minutes, stir occasionally.
Pour in the white wine to deglaze, stir and cook until almost evaporated.
Stir in the cream and fresh thyme, simmer for 3-4 minutes.
Add in 1/4 cup pasta water, truffle sauce and shredded parmesan cheese. Stir to combine and cook for about 1-2 minutes. Taste and adjust seasoning with more salt and pepper. If the sauce is too thick, add more pasta water to create a sauce consistency to your liking.
Serve topped with more fresh thyme, shredded parmesan cheese and ground pepper.
Video
Notes
If you don't have truffle sauce, try substituting with truffle oil or truffle salt - just note you will need to adjust the amount used to your taste. Start with 1 tsp and then go from there.
If you can't find oyster mushrooms you could try using cremini or brown mushrooms.
If you forget to reserve pasta water, you can use vegetable broth instead.