Heat a wok over medium heat. Add oil, and then scallions. Cook, stirring occasionally, until scallions turn golden brown, about 20 minutes. Turn off heat, and let cool in wok. Strain through a fine mesh sieve into a bowl, and let stand until room temperature. Pour into a glass jar, and refrigerate until ready to use. Will keep, at room temperature for up to 1 week, refrigerated for up to 6 months.