For me, there are two types of greens. Kale, turnips, collards, broccoli rabe, mustard greens are tough, assertively flavored greens, while spinach, Swiss chard, and beet greens are milk and tender.
Unlike mild greens, which cook quickly, the more assertive greens must be shallow-blanched before sauteing to remove some of their bitterness. Unless I'm using them to make pasta with vegetables, I usually reserve the more assertively flavored greens for weekend dinners (with pork roast there's nothing better).
Spinach, Swiss chard, and beet greens, however, are a different story. Once cleaned and stemmed, these mild, tender greens cook in just five to seven minutes. My method for cooking them? As I do with the other vegetables in this chapter, I steam/saute them.
To steam/saute tender greens, place two pounds of cleaned spinach, Swiss chard, or beet greens in a large deep skillet, along with a little fat (margarine or olive oil) and seasonings (garlic almost always). Cook the greens, covered, over medium-high heat until they wilt, three to five minutes. Uncover the skillet, and continue to cook until most of the liquid evaporates.
There are two small differences between steam/sauteing vegetables and stem/sauteing greens. First, since tender greens are so moist, there's no need to add the 1/4 cup of water to the pan. Second, use a large, deep skillet to steam/saute the greens. You need a wide surface area so that the liquid evaporates as quickly as possible, and the skillet should be deep enough to hold two pounds of uncooked greens.
If cooking tender greens for more than four, use two skillets or cook them in batches. Twice the amount of greens in the same pan means twice the amount of liquid to evaporate, resulting in overcooked greens.
Although they cook about the same, there are different stemming techniques, depending on the variety and maturity of the green.
For large, mature spinach and beet greens, hold each leaf between the thumb and index finger of one hand while pulling back the stem with the other.
For young spinach and beet greens, hold a bunch by the root, leaf end down, and pinch the leaf from the stem.
For Swiss chard, slash down both sides of each leaf with a sharp knife. Coarse-chop the washed leaves.
How to Cook Without a Book by Pam Anderson.