Cut off the stems of each kale leaf and chop into bite-sized pieces. Wash the kale, leaving it a little wet.
Heat the sesame oil in a large skillet or pot over medium heat. Add the garlic and chili flakes to the hot oil until fragrant, about 30 seconds. Add the kale, stir to coat with the chili and garlic oil (your skillet will overflow with kale at this point, but it’ll wilt considerably). Add the water and cover. Let the kale cook for a minute, then stir the kale and cover again. Cook for 2 more minutes, and when the kale is wilted but still a little crunchy, take off the heat, and stir in the soy sauce, sesame seeds, a pinch or salt and a few grinds of black pepper.
Serve immediately, or let cool and store in an airtight container for up to two days. Cooked kale keeps surprisingly well; simply reheat leftovers in the microwave the day after.