In a large skillet, heat 1 Tbsp. olive oil over medium-high heat. Add sliced sirloin and saute until browned. Transfer to a separate bowl and cover to keep warm.

In same skillet, add the last tbsp of olive oil and heat over medium-high. Saute the sliced mushrooms and onions for 5-7 minutes or until onions are translucent. Transfer mushrooms and onions to bowl with beef and cover to keep warm.

In same skillet, add the butter and melt over medium heat. Add in the flour and whisk together to create a roux. Whisk for about 2 minutes until it bubbles, which means the flour is cooked through. To the roux, add the beef broth and whisk together over medium heat for about 5 minutes until thickened and comes to a low simmer. Add the sherry and Worcestershire and bring back to a simmer. The alcohol in the sherry will cook off.

Once the sauce comes back to a simmer, add the sour cream, garlic salt and pepper. Whisk together until all ingredients become smooth and creamy. To the sauce add the beef, mushrooms and onions, and stir together. Heat on medium low for about 5 minutes.

Serve the stroganoff over cooked egg noodles. The egg noodles can also be stirred into the sauce before serving.

Refrigerate any leftovers in an airtight container for up to 5 days.