Soak your green mung beans in cool water in a large bowl overnight. The beans will double in size so be sure to put in enough water for them to be covered.
In a large pot over medium heat, add drained mung beans, rice, and 10 cups of water to the pot. Add a pinch of salt and raise heat until water comes to a boil.
Lower to a steady simmer (medium-low heat) once the water is bubbling, and stir every few minutes to keep rice from sticking and burning to the bottom.
Keep cooking until the rice breaks down and absorbs all the water, you make need to add more water if the mixture becomes too thick but the rice hasn't broken down yet. I ended up adding about 3 more cups of water, but it might depend on the kind rice you're using or how much liquid the mung beans have absorbed. Just keep some water close by to add as needed (see my video to see the consistency I go for). It typically takes about 30 minutes.
Once the mung beans have cooked through and rice has broken down, turn off the heat and set pot aside.