So, how do I do it? It's delicious and adds a bit of class. Any suggestions as to what I should compose it out of?
I believe you're referring to a compound butter. They usually contain butter and herbs such as sage, parsley, rosemary, thyme, etc., salt, and occasionally lemon, pepper and/or garlic.
For steak it might also include a strongly flavored soft cheese such as a blue cheese such as Gorgonzola or Stilton (my favorite, but my wife hates it).