Preheat the oven to 425°F (218°C). Line a baking sheet with parchment paper and position an oven rack in the middle.
Beat the 3 eggs in a large bowl. Add the cauliflower florets and toss to coat evenly with the eggs.
Put the 1 1/4 cups Panko in a separate shallow bowl. Working in batches if needed, dredge each egg-coated floret in the Panko, pressing lightly so the crumbs adhere. Arrange the coated florets in a single layer on the prepared baking sheet with a little space between pieces.
Bake on the middle rack for 15 minutes. After 15 minutes, move the rack to the upper third of the oven, set the oven to broil, and broil 2–3 minutes until the cauliflower is crisp and golden (watch closely to avoid burning). Remove from the oven.
While the cauliflower bakes, whisk the 2 teaspoons cornstarch with 2 tablespoons of the fresh orange juice until smooth to make a slurry.
Heat a large skillet over medium heat and add the 1 tablespoon sesame oil. Add the grated garlic, grated ginger, and 1/2–1 teaspoon chili flakes and cook, stirring, 1–2 minutes until fragrant. Add the remaining orange juice, the 1/3 cup tamari/soy sauce, 2 tablespoons rice vinegar, and 2 tablespoons honey; bring to a boil.
Whisk the cornstarch slurry into the boiling sauce and cook, stirring, until the sauce is slightly thickened, about 1 minute. Remove the skillet from the heat.
Add the baked cauliflower to the skillet and toss gently to coat with the sauce. If needed, work in batches so pieces are evenly coated.
Transfer the coated cauliflower to a serving dish and garnish with the 2 tablespoons toasted sesame seeds and sliced green onions. Serve immediately.