Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper.

In a large bowl, toss the cauliflower florets with olive oil, salt, and pepper.

Sprinkle the cornstarch over the cauliflower and toss again until each floret is lightly coated.

Spread the cauliflower in a single layer on the prepared baking sheet. Bake for 20-25 minutes, flipping halfway through, until tender and slightly browned.

While the cauliflower is roasting, prepare the sauce. In a small saucepan, whisk together the soy sauce, honey, rice vinegar, sesame oil, minced garlic, minced ginger, and red pepper flakes (if using).

Bring the sauce to a simmer over medium heat. Reduce the heat to low and cook for 3-5 minutes, stirring occasionally, until the sauce has thickened slightly.

Once the cauliflower is done, remove it from the oven. Pour the sauce over the roasted cauliflower and toss gently to coat.

For an extra sticky sauce, you can return the cauliflower to the oven for another 5-7 minutes.

Transfer to a serving dish. Sprinkle with sesame seeds and chopped green onions. Serve immediately.