Preheat the oven to 400° Fahrenheit.
Prepare the cauliflower: remove any leaves from the cauliflower and chop into bite-sized pieces. 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, in a small bowl, stir together the garlic, ginger, soy sauce, maple syrup, rice vinegar, sesame oil and 1 tablespoon cornstarch.
Simmer the sauce: add the sauce to the skillet. Bring it to a boil and then simmer for 2 - 3 minutes, until thickened, stirring frequently. Gently stir the cauliflower into the sauce until coated.
Serve: serve immediately, optionally over rice or noodles. Sprinkle generously with sesame seeds before serving.