Cook Pasta: Boil pasta in salted water until al dente. Reserve 1 cup of pasta water before draining.
Prep: While pasta cooks, whisk together Gochujang, honey, soy sauce, rice vinegar, and sesame oil in a small bowl. Pat steak dry and season generously with salt and pepper.
Sear Steak: Heat olive oil in a large cast-iron or stainless steel skillet over high heat until shimmering. Sear steak for 3-5 minutes per side for medium-rare (130−135∘F), or until desired doneness. Transfer to a cutting board and let it rest for 10 minutes.
Build Sauce: Reduce skillet heat to medium. Sauté shallot until softened (2-3 mins), then add garlic until fragrant (30-60 secs). Pour in the sauce mixture, scraping the bottom of the pan to release browned bits (fond). Simmer for 1-2 minutes.
Combine: Reduce heat to low and melt the butter into the sauce. Add the drained pasta and toss, adding splashes of reserved pasta water until the sauce is silky and clings to the noodles.
Finish: Slice the rested steak thinly against the grain. Add the steak and any accumulated juices to the skillet with the pasta. Toss to combine.
Serve: Divide among four bowls. Garnish with fresh parsley and toasted sesame seeds. Serve immediately.