Whisk the cornstarch, flour, 1 ½ teaspoons vegetable oil, toasted sesame oil, cayenne pepper, salt, black pepper, and ⅓ cup water in a mixing bowl to make a batter. Let it sit for 30 seconds.
Add the cauliflower florets to the bowl and toss to coat them in the batter, adding 1-2 tablespoons of water if needed to loosen the batter enough to toss.
Remove the florets from the batter, letting excess batter drip off, and place them on the prepared baking sheet.
Bake for 30-35 minutes, flipping halfway, until tender and crispy.
Meanwhile, whisk the soy sauce, vinegar, maple syrup, and cornstarch together with ½ cup of water in a bowl or measuring cup. Set aside.
Heat 1 tablespoon vegetable oil in a large, heavy-bottomed skillet on medium.
Add the dried chile peppers and the black peppercorns and cook until fragrant, about 2-4 minutes.
Add the garlic and ginger and saute for 1-2 minutes.
Add the bell peppers and saute for 8-10 minutes until tender.
Pour in the sauce and bring it to a boil. Let boil for 1-2 minutes until slightly thickened.
Add the cauliflower to the skillet and toss gently to coat it in the sauce.
Serve the kung pao cauliflower over rice, if desired, topped with peanuts and scallions.