Set the Instant Pot to Sauté. Add the olive oil and butter. Once melted, add the diced onion and minced garlic. Cook for 3-4 minutes until the onion softens, then add the sliced mushrooms and cook for an additional 2 minutes.: You will notice the pot warming and a faint shimmer forming on the surface of the oil, which is the cue to add fats. The sizzle when you add the olive oil and butter should be immediate and lively; that sound signals the pan is hot enough to brown rather than steam the aromatics. Browning builds flavor through the Maillard reaction, which is why this step matters for a rich sauce. Be careful not to leave the pot unattended, since butter can brown quickly and burn, imparting bitterness. If you smell anything acrid, lower the heat or wipe the base and start again with fresh fats.
Season the beef with salt and pepper. Add the beef in batches to avoid overcrowding and sear on all sides until browned.: When the fats have melted and are shimmering, add the diced onion and minced garlic . You will see the onion edges turn translucent and then a light golden color within a few minutes, and the aroma will shift from sharp to sweet and rounded. This gentle caramelization adds complexity to the finished sauce, helping balance the richness of the beef . Avoid turning the heat too high to prevent the garlic from burning, which would give a bitter aftertaste. Stir frequently for even color.
Sprinkle the flour over the beef and vegetables, stirring for 1 minute to coat them lightly. Pour in the beef broth, Worcestershire sauce, and Dijon mustard, scraping the bottom of the pot to deglaze.: As the onion softens, introduce the sliced mushrooms . They will release moisture and begin to shrink and concentrate in flavor; watch for a change in smell to a deeper, savory note. Mushrooms that are given a moment to brown will contribute a rich, roasted quality to the sauce. A common pitfall is overcrowding, which causes steaming instead of browning. If the mushrooms puddle excessively, give them a little more time to evaporate, or sauté in thinner batches.
Secure the lid and set the Instant Pot to High Pressure for 14 minutes. Once done, perform a quick release of the pressure.: You should see the onion become soft and slightly golden, and the mushrooms reduce and take on color at the edges. The smell at this point turns deeply savory and slightly sweet from the browned aromatics. This aromatic base is crucial for a well rounded sauce because it provides both savory depth and sweetness to offset the tang of the sour cream . Avoid overcooking to the point of dryness, which will rob the dish of moisture and make the final sauce thinner than desired.
Add the egg noodles, making sure they are fully submerged in the liquid. Reseal the lid and cook on High Pressure for 3 minutes, then manually release the pressure.: When you season the beef evenly, the salt starts to draw out surface moisture which helps create a better sear. The sound of pieces hitting the hot surface should be a clear, confident sizzle, not a soft simmer. If you hear more of a wet hiss, the pan is not hot enough and you will not get proper browning. Do not crowd the pot; sear in batches if needed to maintain high heat. Crowding cools the pot and causes steaming, which prevents flavorful browning.
Stir in the sour cream, adding more if you prefer a creamier texture, and adjust salt and pepper to taste. Garnish with chopped parsley if desired.: Watch for deep, caramelized edges on the beef , and a savory, roasted aroma that differs from raw meat. Searing locks in flavor and creates fond on the bottom of the pot that will flavor the broth. If the pieces are pale rather than browned, raise the heat slightly and give them a little more time; just watch to prevent burning. A frequent misstep is tossing the pieces too soon, which interrupts browning. Let them develop color before turning.
Sprinkle the flour over the beef and vegetables, stirring for 1 minute to coat them lightly: As the flour toasts briefly, you will notice a faint toasty scent that signals the raw flour taste is cooking away. This brief toast helps the flour blend smoothly into the liquids later, producing a velvety sauce rather than a raw floury one. Stirring continuously prevents clumping and ensures an even film coats the beef and vegetables. One mistake is adding liquid too quickly; that can create lumps. To avoid this, ensure the flour is well distributed and slightly golden before proceeding.
Pour in the beef broth, Worcestershire sauce, and Dijon mustard, scraping the bottom of the pot to deglaze: When you pour in the beef broth , listen for the hiss as it hits the hot surface and watch the browned fond lift from the pot bottom as you scrape, dissolving into the liquid. Those dissolved bits are flavor gold, essential for a deep sauce. The Worcestershire and Dijon mustard integrate quickly, adding an umami and tangy backbone. If you do not deglaze thoroughly, you risk a burn notice on the Instant Pot or uneven flavor. Take your time scraping well so nothing sticky remains.
Secure the lid and set the Instant Pot to High Pressure for 14 minutes: You will feel the pot building pressure with a faint mechanical hum, and steam will be directed through the valve until it seals. The pressurized environment breaks down connective tissue in the beef , making it fork tender while concentrating flavors. Avoid opening the lid early, as that interrupts the cooking process and can leave beef tougher than intended. A common error is not ensuring the sealing ring is properly seated, which prevents pressure from holding.
Once done, perform a quick release of the pressure: The sudden release produces a rush of steam and a lively hiss; be careful to keep hands and face away. Quick releasing stops cooking immediately, which preserves texture and prevents the noodles or meat from overcooking. If you prefer slightly more tender beef , allow a natural release for a few minutes, but be aware this changes timing and moisture concentration.
Add the egg noodles, making sure they are fully submerged in the liquid: The visual cue here is that the pot should be glossy with a bubbling broth that easily covers the egg noodles . Press the noodles gently so they lie beneath the surface; this ensures even cooking. If noodles are left dry on top, they will cook unevenly and remain chewy. Adjust their placement with a spoon so none poke above the liquid line.
Reseal the lid and cook on High Pressure for 3 minutes, then manually release the pressure: The short, intense burst of pressure cooks the wide egg noodles quickly, and when you release, you should see plump, tender noodles that hold their shape. The texture will be noticeably soft but not falling apart when done correctly. Overcooking will make them mushy, so adhere to the timing and perform a prompt release. A common pitfall is leaving them sealed too long, which causes a gummy texture.
Stir in the sour cream, adding more if you prefer a creamier texture, and adjust salt and pepper to taste: Off heat, fold in the sour cream so it blends into the sauce without curdling, producing a rich, tangy finish with a glossy sheen. The aroma should turn slightly bright and tangy, signaling a harmonious balance of savory and creamy. Taste and tweak the seasoning to let the flavors sing. If the sauce seems too thick, a splash of reserved broth will loosen it gently. Avoid high heat when adding sour cream , as it can split and become grainy.
Garnish with chopped parsley if desired: A scatter of fresh parsley provides a visual contrast and a clean, herbaceous note on the palate. It brightens each bite and adds a final layer of freshness to the rich, creamy profile. Add it just before serving so it stays vibrant and does not wilt.