Prep the steak: Pat steak dry and cut into bite-size cubes. Season generously with salt and pepper. Let it sit while you gather your sauce ingredients.

Cook the noodles: Boil noodles to just shy of al dente. Drain and rinse briefly with hot water if they stick. Toss with a few drops of oil to prevent clumping.

Mix the sauce: In a small bowl, whisk together soy sauce, oyster sauce, mirin or rice vinegar, brown sugar or honey, and sesame oil. Add red pepper flakes if using. Taste and adjust for salt, sweetness, and tang.

Sear the steak: Heat a large skillet or wok over medium-high until very hot. Add oil, then the steak in a single layer. Don’t crowd the pan. Sear 1 to 2 minutes per side until browned and medium-rare to medium. Remove to a plate and keep warm.

Build the garlic base: Reduce heat to medium. Add 2 tablespoons butter to the same pan. Once melted and foamy, add the minced garlic. Stir constantly for 30 to 60 seconds until fragrant, not browned.

Toss the noodles: Add cooked noodles to the garlic butter. Pour in the sauce and toss with tongs until the noodles are glossy and evenly coated, about 1 to 2 minutes. Add the last tablespoon of butter for extra sheen.

Finish with steak: Return the steak and any juices to the pan. Toss quickly to warm through. Squeeze a little lemon over the steak if you like, then fold in most of the green onions.

Garnish and serve: Top with remaining green onions and sesame seeds. Serve hot, with extra chili oil on the side.