Select saute on instant pot. Heat oil for 1 min. Add onion and 1/2 tsp salt. Cook and stir until begins to soften, 3-4 min.

Season beef with 1tsp salt and pepper. Add to pot. Cook and stir until browned on all sides, about 2 min. Add garlic and thyme. Cook about 30 seconds. Pour in soy sauce.

Stir mushrooms into the pot. Stir in flour. Pour in stock and 1/2 tsp salt. Close and lock the lid. Set timer for 10 min. Set to high pressure for 10-15 min.

Release pressure. Open pot. Add noodles. Seal and bring to high pressure again, about 5 min. Cook for 5 min. Release pressure naturally for 5 min. Release remaining pressure using the quick release method. Open pot. Stir in sour cream