To make the sauce: 

1. In a small saucepan, heat the sesame oil over low heat. Add the ginger and garlic, stirring to coat in the oil. Let them soften for about 10 minutes, stirring occasionally—don’t let them brown.
2. Add the white parts of the scallions and sauté over medium heat for about 2 minutes, until fragrant and softened.
3. Increase the heat to medium-high. Once the pan starts to sizzle, deglaze with mirin.
4. Add the broth, sugar, soy sauce, and rice vinegar. Bring to a gentle boil.
5. Stir in the cornstarch slurry and whisk until the sauce thickens. Remove from heat and let it cool slightly.

To prepare the cauliflower: 

1. In a mixing bowl, whisk together the rice flour, all-purpose flour, cornstarch, and salt. Slowly pour in 3/4 cup of cold fizzy water, stirring until smooth. Add more water, a tablespoon at a time, if the batter feels too thick. It should cling to the cauliflower without dripping off.
2. Bring a large pot of water to a boil. Add the cauliflower florets and blanch for 4 minutes. Remove with tongs or a skimmer and transfer to a clean dish towel. Gently press to remove excess moisture without breaking the florets.
3. Add the cauliflower to the batter and gently mix by hand to coat evenly.

To fry:

1. In a deep, heavy-bottomed pot, heat several inches of canola oil over medium-high heat. After about 7 minutes, test the oil by dropping in a bit of batter—it should bubble immediately. (The oil should be between  350°-375°F—feel free to use a thermometer if you’d like.)
2. Working in small batches, carefully lower the battered cauliflower into the oil. Use tongs or chopsticks to stir gently so they don’t stick. Fry for several minutes, until golden and crisp with craggy edges.
3. Transfer to a paper towel-lined plate or wire rack to drain.

To serve:

1. Toss the fried cauliflower in the warm sauce until well coated.
2. Serve over rice and top with reserved green scallions, chopped peanuts, and chilies or habanero powder. Serve immediately.