Place cauliflower florets in a microwave-safe bowl. Cover the bowl with a damp paper towel and microwave for 1 minute. (This will get the florets started cooking, but they should still hold their shape.)
Whisk together rice vinegar, 1 Tbsp soy sauce, cornstarch, and salt. Pour over cauliflower florets and toss to coat. Set aside.
Make sauce by whisking together ginger, garlic, water, 2 Tbsp soy sauce, hoisin sauce, honey, toasted sesame oil, and red pepper flakes.
Heat peanut oil in a wok or skillet over medium heat. Add peanuts and fry in oil until they start to turn golden, Use a slotted spoon to transfer peanuts to a paper-towel lined plate. (Leave the wok with oil over heat.)
Use a spoon to toss cauliflower florets in cornstarch mixture once more to fully coat them.
Use a slotted spoon to transfer cauliflower to the hot oil. (Note: Test this with one small cauliflower floret. If the oil pops / spits, turn the heat down a bit and wait a minute to add the remaining cauliflower.)
Gently fry the cauliflower, stirring occasionally, until golden brown, about 5 minutes.
Drain off oil, leaving cauliflower in the wok.
Pour sauce over cauliflower. Simmer until sauce thickens, about 2 minutes.
Stir in peanuts and green onions.
Serve over rice.