From Tender by Nigel Slater - Enough for 2 as a side dish
I was very happy to find a chapter devoted to Chinese Greens in this cookbook!  He suggests it would be an excellent side for a mushroom stir-fry.

1 bunch Bok Choy
1/2 bunch of Mustard
2 large Garlic Cloves OR use some of the fresh Green Garlic, including some of the tender green tops
Ginger, a thumb sized piece
6 Green Onions, OR use the Spring Onions, green tops included
2 TB Peanut Oil
1 TB Thai Fish Sauce

Bring a saucepan of deep water to a boil and salt it lightly.  Wash the greens thoroughly.  Peel the garlic and ginger, finely chop the garlic, and shred the ginger into matchstick-like strips.  Trim the green onions and cut each into two or three.Warm the oil in a shallow pan or wok.  Toss the garlic, ginger, and green onions in the oil until deep gold, verging on being lightly browned and fragrant.  Drop the greens, whole or shredded as you wish, into the boiling water.  Leave for only a minute or so before draining.  Pour the fish sauce in with the garlic and ginger, it will spit and sizzle, then toss with the greens and eat.