The "crack sauce" in this recipe is a working home cook's version of nam jim, the bright, funky, fiercely balanced dipping sauce that shows up across Thai cuisine. Fish sauce, soy, brown sugar, lime, garlic, and chili flakes, whisked together off heat. It's the kind of sauce that turns almost any grilled or seared protein into something memorable.
The trick is making it directly in the pan where you just seared the steak. Turn off the heat but don't move the pan. Add all the sauce ingredients to the hot fond and fat left behind by the steak. The residual heat emulsifies everything and pulls in the browned meat flavor that would otherwise be wasted. Ten seconds of whisking and the sauce is done.
The steak itself is a straight sear. Sirloin or flank, heavily seasoned, hot pan, don't move it until a hard crust forms. Flip once, pull at medium rare, rest. Letting it rest before slicing is non-negotiable; the juices need to redistribute or they end up on the cutting board instead of in the meat.
The noodles are a different kind of decision from most of the dishes in this collection. They're aromatic rather than saucy, built on ginger, garlic, and scallion whites with a light noodle seasoning. They're a vehicle for the crack sauce, not a competitor to it. Keep them savory but not wet. Too much liquid and the noodles will overpower the steak and the sauce.
Plate with the noodles as a bed, sliced steak on top, crack sauce on the side in a small bowl. Serving the sauce on the side is important. If you pour it directly over, the saltiness dominates. A small dip of it per bite is exactly the right balance.