This is a wonderful, rich dish which can be made mostly from pantry staples. It takes almost no time to make, yet tastes like you spent a lot of time on it. It's also versatile- I use this sauce (without the sour cream) for Salisbury Steak. If you want to take it upscale for company, try using sliced beef tenderloin. It's also a great way to use up leftover beef, just cut into thin strips, skip the steps regarding cooking the beef, and add it into the sauce a few minutes before serving so it has time to heat through.