Wow what flavours ...Can't say I have used walnuts and beef,turned out that pulling some beef out of the freezer a bag of chopped walnuts the wife uses for her amazing banana bred, fell on the floor,I picked up and figured ,hey why not. Turned out to be a fantastic combination very simple top prepare

Here is whats needed
2-top sirloin steaks,or any other steaks about 6 oz each
3oz- chopped walnuts 
2oz- butter
Cracked black pepper
1 frying pan 
.5oz-veg oil

Heat up a frying pan that can go into the oven, add the veg oil, once heated add the steaks that have been previously seasoned with salt and patted down with cracked black pepper on both sides, pan sear on both sides to seal all the juices in,once complete place in the oven that has previously heated to 400 F. Depending on the thickness of the meat it should not take more than 10 minutes for medium rare,remove from the oven and set the steaks aside on a plate covered with a cloth . 
While the meat rests ,place the pan on top of  a burner on medium heat (remember that the pan is very hot from the oven) add the butter ans the walnuts, stirring until the butter turns a little brown, here you might want to add a little slash of  freshly squeezed lemon juice and the drippings from the beef 
The beef used was a couple of  top sirloin steaks from Spring Creek Ranch,possible the best beef anywhere,here is a link to their site