I think of this as elegant comfort food. As it happened, I had a chunk of beef tenderloin in my freezer, so that's what I used this time. Other times I have used a less expensive cut of meat, like chuck roast, and cooked it longer (about 3 hours, before adding the sour cream mixture). If you use the tenderloin, the timing is touchier than if you use a tougher cut. The latter gives you more wiggle room to make it in advance and let it sit on the stove a bit over low heat. Use the tenderloin if you'll be able to go straight from stove to table with no waiting or distractions.
Adapted from from Craig Claiborne