Cucumbers are slightly pickled before being stir-fried, giving them a wonderfully crunchy and chewy texture. And the raw cucumber taste is nicely smoothed out by the cooking process.
If you like mushrooms, you can also add some sliced mushrooms to the ground beef. When the beef is nice and hot, turn the heat off and let it wait until you get the cucumber ready.
Squeeze out excess water from the cucumbers. You can just take a handful in your hands and squeeze the water out as much as you can (the more you squeeze the liquid out, the crisper the cucumbers will be). You can also use a cheese cloth to wring out the liquid.