Prepared in 15 minutes or less plus 1 day to marinate.
In a medium saucepan over medium-high heat, add oil.
Add bok choy, and cook, turning once, until just beginning to turn golden, about 2 minutes.
Add stock and soy sauce. Cover; reduce heat to medium, and simmer until bok choy is tender, about 5 minutes.
Transfer bok choy to a serving platter, reserving cooking liquid in skillet.
Cook liquid over medium-high heat until it is reduced by half, 1 to 2 minutes. Pour over bok choy, and serve. Serves 4.