Follow the package instructions for cooking the pasta. Drain and set aside.
Add the oil to the skillet over medium heat. Once hot, saute the onion until translucent, about 4 to 6 minutes.
Add the mushrooms, spices, and herbs. Cook for 7 to 10 minutes, stirring occasionally, until the mushrooms begin to shrink and brown.
Add the garlic and cook for another minute, stirring occasionally.
Add the mustard and vinegar. Saute for another 3 minutes.
Slowly sprinkle the flour, stirring constantly for 1 to 3 minutes until the sauce thickens. Adjust the consistency with water if needed.
Spoon your mushroom stroganoff over the drained pasta. Garnish with parsley. Enjoy!
Notes
Instead of soaking the mushrooms in water to clean them, just wipe them with a damp cloth! Also, ensure they are completely dry before adding them to the pan so they don't get slimy and rubbery.
Another reason why mushrooms get rubbery is if they're steamed instead of seared in the pan. You want the mushrooms to have enough space in the pan so they can brown beautifully.
You don't need to stir the mushrooms constantly when cooking them. Just stir every few minutes to allow them to release their juices and get a nice sear for the perfect flavor and tender texture.