Wash the broccoli and shake off excess water. (You want some water still clinging to the leaves, as that will help with the cooking process.)
Chop the stalks into 1-inch pieces and set aside. Chop the leaves into bite-size pieces.
In a small bowl, mix the oyster sauce, water, fish sauce and stevia.
Heat a wok or large skillet over a high flame. Swirl in the oil. Add the garlic and stir briefly, until sizzling and fragrant. If the stalks are very thick, add them to the pan first, stirring for 1-2 minutes before adding the leaves. Otherwise, add both stalks and leaves to the pan, followed by the sauce. Stir and toss the vegetables frequently until the leaves are wilted and the stalks are tender, about 3-5 minutes.
You can add a protein like shrimp, chicken or tofu to the stir-fry. Increase the amount of sauce and stir-fry the protein for a few minutes before adding the garlic.