Preheat the broiler to high. Line a baking sheet with parchment.
In a large bowl, toss the cauliflower with 1 tablespoon cornstarch to coat. Add the coconut milk and 2 tablespoons soy sauce, tossing to evenly coat all the florets. Spread the cauliflower in an even layer on the prepared baking sheet. Transfer to the oven and broil for 3-4 minutes, until the cauliflower is just beginning to char on the edges. Reduce the oven temp to 425 and bake another 5 minutes, until just tender.
Meanwhile, make the sauce. Combine the remaining 1/3 cup soy sauce, hoisin sauce, honey, vinegar, crushed red pepper flakes, and a pinch of pepper.
Add 1/4 cup water and the remaining 1 tablespoons cornstarch, whisking until combined and smooth.
Heat the oil in a large skillet over medium heat for 1 minute. Add the garlic, ginger, and cook until fragrant, about 30 seconds. Stir in the soy sauce mixture and bring to a boil over medium heat. Once boiling, reduce the heat to low. Add the cauliflower and cook, stirring occasionally, until the sauce thickens slightly, about 5 minutes.
Serve the cauliflower and sauce over bowls of rice. Top with additional peanuts and green onions. Enjoy!