Breasts have such a nice, round, comforting shape. It just seemed a natural logical step to make breast hand warmers from the cashmere sweater.
Step 1: Obtain and felt cashmere
Comb the local thrift stores and look at the labels. I avoid the synthetic fiber blends. If you're lucky enough to score a 100% cashmere sweater in a flesh tone, take it home and wash it in hot water. Sure, the care label will say ridiculous things like "dry clean only" or "hand wash in cold water" or "lick clean," but just ignore them. I was unimpressed when I first touched 100% cashmere; it just didn't feel that soft. After it was felted, though, I was smitten. Washing wool in hot water with a little soap makes the fibers get crinkly and cling to each other. This makes the holes in the knit smaller and fluffs out the texture quite a bit.
Cashmere takes longer to felt than other types of wool. Check the sweater after you've washed it once. If it hasn't shrunk much and isn't very fuzzy, wash it again. Most people have to run cashmere sweaters through at least 3 hot water washing machine cycles.