Take your pan-seared steak to the next level.
You may want to avoid attempting this if you're cooking steak in a cast iron pan. You really need a heavy-bottomed stainless steel 12" skillet. You of course need the heavy-bottom to get good sear on the steak, but you also need a material that will not react with the high acidity of the wine.
Cook a steak in a 12" skillet using any method that you prefer, as long as it produces some crusty brown fond on the bottom of the pan when you're done. Set your steak(s) aside to rest, and clear the pan of any debris (herbs, garlic, etc) and excess fat (you only need about a tablespoon for this recipe).
Return the pan to medium heat, add shallot, and cook until softened (about 3 minutes).
Add garlic, and cook until fragrant.
Using a balloon whisk, deglaze the pan with red wine (whatever you're drinking with the steak), scraping up any brown bits, until the wine starts to dry up.
Add chicken stock, and scrape up any remaining brown bits from the bottom of the pan. Reduce again until slightly thickened. You can accelerate the process by continuing to whisk, producing as much steam as possible.
Take the pan off the heat, and add butter. Whisk until thoroughly combined and glossy.
Pour over your steak, or serve on the side.