AKA Bul kogi, Bul-kogi, Boolgogi, Bool gogi, Bulgogi. No matter how you spell it, it's seriously good eats.
This is adapted from the book Quick and Easy Korean Cooking by Cecilia Hae-Jin Lee. I think the recipe in the book is under-seasoned, so here is my modified version.
The first thing you have to do is figure out where to get some nice, marbled, rib-eye steak, "thinly sliced".
Ideally, you want it sliced about 1/8 inch thick. This is pretty hard to do with a knife, but is an easy job for an electric meat slicer.
A lot of places won't do it for you because of the cleaning of the slicer that's involved.
But, if you have an electric slicer, it's easy to do yourself:

Gently toss the sliced beef with 4 T soy sauce, 4 t sesame oil, 2 T sugar, black pepper, and garlic, in a large mixing bowl.
Cover with plastic wrap and refrigerate overnight.
Set aside 1T soy sauce, 1 t sesame oil, and 1 T sugar.
Heat your largest** non-stick skillet over medium-high to high heat.
Add 1/4 of the beef and stir-fry until completely browned and caramelized around the edges.
Remove to a dish and set aside.
Repeat until all the meat had been cooked.
Crank the heat up to high and pour all the meat back into the skillet.
Add the remaining soy sauce, sugar, and sesame oil and cook until everything is hot and caramelized.
Remove to a serving dish and sprinkle with toasted sesame seeds and sliced green onions.
Serve immediately with rice and kimchi and Korean pickled peppers.
* Mince. Don't use a garlic press or micro-plane. A mini-chop works great.
** If your largest non-stick skillet is less than 10", cook it in smaller batches. I have an El Cheapo 14" skillet from Sam's that I love.
The Johnson Family Cookbook