Preheat the oven to 400° Fahrenheit.
Prepare the cauliflower: remove any leaves from the cauliflower and chop into bite-sized florets. In a medium bowl, toss the cauliflower with the oil. Then toss the cauliflower with 2 tablespoons of cornstarch.
Bake the cauliflower: place the cauliflower in one layer on a foil or parchment paper lined baking sheet. Bake for 10 minutes, flip and bake for 5 - 10 minutes more, until the cauliflower is browned and cooked through.
Make the sauce: as the cauliflower cooks, make the sauce. In a small bowl, stir together all of the ingredients for the sauce.
Cook the sauce: add the sauce to a medium skillet over medium-high heat. Bring the sauce to a boil, turn down the heat to medium-low and simmer for 4 - 5 minutes, stirring frequently. The sauce should bubble, thicken and reduce.
Serve: add the cauliflower to the skillet and gently toss in the sauce. Serve immediately, optionally with a side of white rice and topped with green onions & sesame seeds.