There's been a lot of rumor about the origins of this dish; I'll let others fight it out and just focus on its deliciousness! I think that the human palate is drawn to the combination of savory, sour, sweet, salty and spicy. I think that's why we all love this dish. There's a huge difference between the popular sambal oelek and Chinese chili garlic sauce. Sambal is very easy to find but it's twice as hot as chili garlic. So, if you are using sambal, use half the amount.
For the Sauce: Add all of the sauce ingredients into a 1-quart (946-ml) saucepan, and bring the heat up to medium. Whisk gently as it comes to a simmer. Allow it to simmer and keep whisking it for about 5 minutes, until the sauce thickens. Remove from the heat and reserve it.
For the Chicken: Heat the 1 1/2 quarts oil in a 4-quart (3.8-L) Dutch oven to 375 degrees F (190 degrees C) using a frying thermometer. Rinse the chicken in cold water and pat dry with paper towels. Mix 11/2 cups (335 g) of the tempura flour and 1 cup (240 ml) water into a thick batter. It should look like thick pancake batter. Dredge the chicken cubes in the remaining 1 cup (223 g) of tempura flour and fry them in two batches until golden brown and crispy, about 6 to 8 minutes. Drain the chicken on paper towels or a wire rack.
Heat a wok or large skillet to high and add 2 tablespoons (30 ml) of oil. When you see the first wisps of white smoke, stir in the fried chicken, onion, chiles and broccoli and cook them for about 30 seconds. Stir in the sauce and allow it to coat the chicken and simmer. Cook it, folding all the ingredients until they are well coated, about 2 minutes. Garnish with the scallions.
Adapted with permission from "101 Asian Dishes You Need to Cook Before You Die" by Jet Tila, Page Street Publishing Co. 2017. Photo credit: Ken Goodman