Soondubu comes in plastic covered, tube-shaped packages OR plastic sealed boxes. Look in the tofu section at the Asian market. Korean Soft Tofu goes by many names: Soondubu, Soon Tofu, Soft Silken Tofu or Extra Silken Tofu.
If your Soondubu comes in a plastic tube, look for a dotted line. That dotted line tells you where to cut, but don’t cut all the way through! Cut halfway, then open the package like a hinge. Once opened, spoon or squeeze the extra silken tofu directly into the cooking pot.