Preheat oven to 425°F. Make sure your oven is fully preheated before putting anything in — this ensures even baking from the very first minute.
Dip cauliflower in egg, then cornstarch.
Bake on parchment 25-30 minutes until crispy. Every oven is a little different, so start checking a few minutes early. You're looking for a golden color and a wonderful aroma filling your kitchen.
Meanwhile, combine soy sauce, vinegar, sugar, hoisin, and sesame oil.
Sauté garlic, ginger, and red pepper flakes. Always taste as you go — you can add more seasoning, but you can't take it away! Make sure your pan is properly heated before adding ingredients — you should hear a nice sizzle. Don't overcrowd the pan or things will steam instead of getting that beautiful golden color.
Add sauce mixture and simmer 2 minutes. Keep an eye on the heat — you want a gentle simmer with small bubbles, not a rolling boil. This helps develop flavor without overcooking.
Toss crispy cauliflower in sauce.
Garnish with green onions. This is your chance to make it look as good as it tastes! A little garnish goes a long way for presentation.