Begin by heating 2 tablespoons of olive oil in a large skillet over medium-high heat. Once the oil shimmers, add the thinly sliced beef in a single layer, ensuring not to overcrowd the pan. Sear the beef for about 5 minutes, turning occasionally until browned on all sides. Once done, remove the beef from the skillet and set it aside on a plate.

In the same skillet, add the finely chopped onion and minced garlic. Sauté over medium heat for about 3 minutes, stirring frequently until the onion becomes soft and translucent. Next, add the sliced mushrooms; cook for approximately 5 minutes until they release their juices and begin to turn golden brown.

Return the seared beef to the skillet with the cooked onion and mushrooms. Pour in about 1 cup of beef broth and stir in 1 tablespoon of Dijon mustard, combining everything well. Scrape the bottom of the skillet to incorporate any browned bits for extra flavor. Allow the mixture to simmer for 5 minutes.

Once the sauce has simmered and thickened, remove the skillet from heat. Stir in about 1 cup of sour cream until the sauce is smooth and creamy. Taste the sauce and season with salt and pepper to your liking.

While the sauce is resting, cook your choice of egg noodles, mashed potatoes, or rice according to the package instructions. Once they are ready, plate the base and generously spoon the Homemade Beef Stroganoff on top.