Prepare the lettuce: Remove core, separate leaves, rinse in cold water, then thoroughly dry in a salad spinner or by patting with clean towels. Tear leaves by hand into bite-sized pieces to preserve texture.
Slice scallions: Trim roots and thinly slice on a bias. Set aside.
Make the dressing: In a small bowl or jar, combine grated garlic, soy sauce, rice vinegar, sugar (or honey), toasted sesame oil, neutral oil (if using), fish sauce (if using), and gochugaru or minced chili. Whisk or shake vigorously until sugar dissolves and the mixture is slightly emulsified. Taste and adjust (more vinegar for brightness, more sesame oil for aroma, more soy/fish sauce for saltiness).
Toast sesame seeds (if not pre-toasted): In a dry skillet over medium heat, toast seeds for 1–2 minutes until fragrant, stirring constantly. Let cool and lightly crush if desired.
Toss the salad: Place dried lettuce in a large bowl. Add sliced scallions and most of the sesame seeds. Drizzle about two-thirds of the dressing over the greens (you can add more later). Gently toss with clean hands or tongs, coating leaves evenly without crushing them.
Taste and finish: Sample a leaf. Add more dressing, a pinch of salt, or black pepper if needed. Finish with a final light drizzle of sesame oil (for aroma) and a sprinkle of remaining sesame seeds.
Serve immediately: Best served right away so the lettuce keeps its crisp texture. If serving as part of a spread, dress only right before plating.