I've heard you should do this when harvesting lettuce so you can get a 2nd harvest. What varieties of lettuce should you use this method with? Should you wait until the lettuce is fully mature to allow the head to grow back, or can you do this earlier in the growing cycle with lettuce?

If so, when? Also, does it matter how you harvest the lettuce with this method?

The variety I'll be growing is a miniature variety that has the texture of bibb lettuce and the taste of romaine.