Season beef with salt and pepper. Sprinkle garlic powder over beef, tossing to coat. Set your Instant Pot to sauté on Normal. When the display says Hot, add 2 tbsp oil and heat until shimmering. Working in batches, add beef and cook, stirring, for 3 to 5 minutes or until browned on all sides, adding more oil as needed between batches. Using a slotted spoon, transfer beef to a plate as it is browned.
Add 3 tbsp butter to the pot and heat until melted. Add onion and mushrooms; cook, stirring, for about 10 minutes or until onion and mushrooms are softened and liquid is evaporated. Stir in broth and Worcestershire sauce. Press Cancel. Return beef and any accumulated juices to the pot, stirring well.
Close and lock the lid and turn the steam release handle to Sealing. Set your Instant Pot to pressure cook on High for 15 minutes.
Meanwhile, in a large pot of boiling salted water, cook egg noodles according to package directions. Drain. Transfer to a bowl and toss with remaining 1 tbsp of butter. Set aside.
When the cooking time is done, press Cancel and let stand 3 minutes. Then turn the steam release handle to Venting. When the float valve drops down, remove the lid. The beef should be fork-tender. (If more cooking time is needed, continue pressure cooking on High for 3 minutes.)
Stir ½ cup liquid from the pot into the sour cream and then stir into the remaining ingredients in the pot. (see tip) Set your Instant Pot to sauté on Normal. Cook, stirring, for about 3 minutes or until sauce is thickened.
Season stroganoff to taste with salt and pepper. Serve over buttered noodles.