Gobhi Manchurian - Cauliflower Manchurian

This is an Indo-Chinese recipe, that's very popular all across India. Cauliflower is known as Gobhi in Hindi.
I heard a funny story about a pure vegetarian software engineer in India, who was sent to China on an assignment. Being vegetarian, your options are pretty much limited in China. This guy confidently accepted the assignment, thinking that he can order Gobhi Manchurian and survive. To his horror, there is no such thing as Gobhi Manchurian or Gobhi Anything in China! This is a vegetarian dish using common Chinese ingredients and techniques, but only found in India. ;-)

Ingredients:

Cauliflower - 1 medium
All purpose flour - 1/2 cup
Corn Starch - 1/4 cup
Soy Sauce - 5 tbsp
Salt - to taste
Pepper - 1 tsp
Yellow onion - 1 medium, minced
Garlic cloves - 3, minced
Freshly grated ginger - 2 tsp
Coriander powder - 1 tsp
Red Chilli powder - 1 tsp
Rice vinegar - 2 tsp
Siracha sauce or Sambal Olek - 1 tbsp
Maggi Hot and Sweet Tomato sauce - 1/4 cup (substitute: 1/2 cup tomato puree)
Apricot Jam - 2 tbsp (Substitute: 1 tsp sugar)
Vegetable oil - 1 tbsp, plus more for frying
Green Onion (spring onion) - 1 stalk, minced

Method:

Wash cauliflower florets. Preheat the oven to 425 degrees F. Arrange the cauliflower on an oiled baking sheet, season with salt and pepper to taste, and roast until just tender, turning once, 12 to 15 minutes total. Remove from the oven and set aside. Reduce the oven temperature to 325 degrees F.
In a bowl, combine the all-purpose flour and cornstarch. Add 1/2 teaspoon of the coriander, 1/2 teaspoon of the red chilli powder, and 1/2 teaspoon each of salt and black pepper. Stir in 2 tablespoons of the soy sauce and the water and mix well to make a batter. Add another tablespoon or so of water if the batter is too thick.
In a large skillet, heat a thin layer of oil over medium-high heat. Working in batches, dip the cauliflower in the batter, then arrange in the hot skillet. Fry until golden brown, turning once, 4 to 5 minutes total. Optionally, you can also deep fry it. Transfer the cooked cauliflower to the baking sheet and return to the oven to keep warm.
Heat the 1 tablespoon oil in a skillet over medium-high heat. Add the onion and cook until softened, about 5 minutes. Add the garlic, ginger, 1/4 teaspoon salt, the remaining 1/2 teaspoon coriander, and remaining 1/2 teaspoon red chilli powder, and cook 1 to 2 minutes. Stir in the 1 tbsp apricot jam, 3 tablespoons soy sauce, 2 tsp rice vinegar, Sriracha (or Sambal Olek), Maggi hot and sweet tomato sauce (or tomato puree). Add 3 tablespoons of the Spring Onions and cook, stirring, until the sauce is thickened and the flavors have blended, about 5 minutes. Add up to 1/4 cup of water is the sauce is too thick. Taste and adjust the seasonings.
Return the fried cauliflower to the pan and spoon on the sauce to coat, turning the cauliflower gently to coat with sauce. Serve immediately. Garnish with the remaining 1 tablespoon green onions.