Marinate the chicken with cornstarch and salt. If the chicken is too dry, add a little water to ensure each piece is nicely coated with the cornstarch.
Heat up a pot of water and bring it to a boil. Cook the broccoli for 1 minute, then drain and set aside.
Heat up a wok or skillet on high heat and add the oil. Once the oil is heated, add the garlic and stir-fry until aromatic or lightly browned. Add the chicken and give it a few quick stirs. Then, add the sauce and reduce the heat to low.
When the chicken is cooked through, add the broccoli and stir to combine well. Dish out and serve immediately.
Notes
Don't overcook the broccoli. The broccoli should be crunchy and have a bite.