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