Natto is a Japanese food made of fermented soybeans. While natto is rich in nutrients, many people are put off by its strong odor and residual bad breath. If you have a taste for natto, making it is a straightforward process.
Make natto with a combination of packaged natto with dried soybeans and water. According to bento.com, use the packaged natto as a starter culture. If you have rice straw, use that instead of packaged natto.
Prepare dried soybeans for natto by soaking, straining and cooking in a pressure cooker. When this phase is finished, bento.com warns you not to open the pressure cooker lid. Cool the pressure cooker by slowly releasing steam and cooling in water.
Work with the soybeans in a fully clean--including your hands--environment and with a sterilized spoon. Add the starter natto to the cooked beans. According to bento.com, by a series of steps that include cooling, mildly heating and allowing the starter to blend with the freshly cooked soybeans, your homemade natto will be ready in 24 to 48 hours.