Blanch broccoli in boiling salted water for 1-2 minutes until bright green and tender-crisp. Drain and rinse under cold water to stop cooking. Drain or pat dry well.
In a bowl, mix soy sauce, sesame oil, toasted sesame seeds, sugar, garlic and rice vinegar. Add the broccoli and toss gently to coat.
Sprinkle with additional sesame seeds and gochugaru if using. Let sit for 10 minutes to absorb the flavors before serving. Serve chilled or at room temperature.