Pour the milk into two bowls. Cover with foil and steam over high heat 5 minutes. Remove from the heat, remove the foil and let cool. When the surface layer has set, flip up a corner and pour out the milk into an empty bowl.
Whisk the egg whites with the sugar. Pour in the milk and mix well. Pour the liquid back to the 2 bowls under the set milk layer. Cover with foil again and steam over high heat until set, about 15 minutes. Serve warm or cold.