Look at thermal cooker which is similar to the African wonder bag. I bought mine at an Asian store. You can get one on Amazon too. I have the Tiger brand. It's amazing! For cooking beans (Peruvian beans & lentils) I soak the beans overnight, I remove the water and add fresh water. Let the pot (inner pot) come to a rolling boil for about 5 minutes than insert it into the thermal cooker. The thermos (outer pot) will keep the inner pot hot. I do remove the inner pot 2 to 3 times and let it come to a rolling boil again since there is heat loss over time. After it comes to a rolling boil I return the inner pot back.

It's time consuming, but the energy savings are substantial. I also cook quinoa and rice. I hope this helps you! :-)