30 minutes. Barley and mung beans have a hard texture and are not easy to boil. Before making soup and porridge, soak barley and mung beans in cold water for about 2 hours in advance. Then put the barley and mung beans into the pot together. After boiling over high heat, continue to cook over medium-low heat for 30 minutes. It is ready to eat. The cooked barley and mung beans are relatively soft and easy to digest and absorb.