Let’s start with the bulgogi marinade! In a mixing bowl, whisk together the ginger, garlic, crushed red pepper, black pepper, sugar, sesame oil, soy sauce, scallions and sesame seeds. Briefly set aside.
Slice your steak against the grain as thinly as possible. (Popping the steak in the freezer for 20 minutes will make it easier to get thin slices.)
Add the steak to the bowl and use your hands to massage the marinade into the sliced beef, making sure each piece is well coated. (Yes, this is kind of gross, but also fun.) Cover the beef with plastic wrap and refrigerate for at least 30 minutes or overnight. Obviously, the longer you marinate, to more tender and flavorful your bulgogi will be.
Meanwhile, make your slaw. In a medium bowl, whisk together the vinegar, oil, sugar, and a pinch of salt. Add the cabbage, carrots and radishes, and toss to coat. Cover and refrigerate until ready to use.
In a medium bowl, whisk together all the ingredients. Cover and refrigerate until ready to use.
Now it’s time to cook the bulgogi. Heat a large saucepan (or wok) over high heat. When hot, remove steak from the marinade and add it to the pan in a single layer. (Depending on the size of your pan, you’ll need to pan-fry the meat in 2-3 batches.) Let it sear (don’t move it!) for about 2 minutes. Stir the beef and continue cooking for another 3-5 minutes until it’s well done and nicely browned.
Fry your eggs (if using).
To assemble your bulgogi sandwiches: Pile bulgogi onto the each roll. Top with slaw, fried eggs, and creamy-spicy sauce. Serve immediately.