Rinse mung beans and place them in a large glass bowl. Cover with enough filtered water to allow the beans to roughly double in size as they expand. Leave on the counter for 8 hours or overnight.

Drain the soaking water and place beans in a large pot. Cover with fresh filtered water.

Bring the beans to a boil, turn down the temperature to a simmer, affix the lid and cook the beans for about 20 minutes until just soft but not mushy (do not overcook!).

Drain the beans and place in a large VitaClay slow cooker or crockpot. The beans should be no more than 1" in depth. Discard any beans that may accidentally spill during the transfer from the pot to a VitaClay (or other slow cooker).

Let the beans cool for 10 minutes in the Vitaclay.

While the beans are cooling slightly, dissolve a packet of natto starter in 3 Tbsp of warm filtered water.

Pour the natto spore solution over the cooled but still warm beans. Stir gently to mix with a clean, bamboo spoon.

Place the lid on the VitaClay and select the "yogurt" setting.

If using a different type of slow cooker, use the setting that will keep the beans between 100-110 °F/ 38-43 °C which is the temperature range necessary to ferment the beans into natto.

After 24 hours, turn off the Vitaclay, remove the lid, and cool the natto to room temperature for 1 hour. A whitish film and an ammonia-like aroma means they are done. The beans will also have a stringy and slimy appearance (see photo above).

Place the cooled natto in a glass container with a tight-fitting lid and refrigerate.

Natto will be ready to eat once refrigerated overnight. It will last for months, and the flavor will age and strengthen with time.

Mung beans contain less than 1% of the isoflavones in soy. Thus, feel free to eat 1-3 tablespoons per day of mung bean natto for an inexpensive and tasty soil-based probiotic and Vitamin K2 food source.