Bring your steak up to room temperature. Admire it. Try to avoid touching it too much with your hands as your body heat will begin rendering the fat.
Apply very little salt and pepper. Use photo for reference. Bring stainless steel pan to medium high or high heat. Do NOT add any butter or oil to the pan.
Place the steak in the pan. Depending on thickness and the pan temp, anywhere from 30 seconds to 3 minutes. The side that is in contact with the pan should be nicely caramelized when you flip it.
Finish cooking for about 75% as long as the amount of time needed on the first side. Use an instant read probe if you need to. I'd let it get to at least 130 before pulling and I'd suggest closer to 135. It will continue to rise a bit after you do. Now I know some steak pros out there are going to say that is overcooked. But for an A5 Wagyu striploin, you must fully render the fat or you're going to have a chewy piece of meat instead of melt in your mouth goodness.
You can see the melted fat not only in the pan, but splattered all over the stove. This is all naturally from the steak!
Let the steak rest a few minutes before slicing it into 1/2" to 3/4" strips. Savor every bite!!!!