Adjust amounts to fit what you feel like eating. For a small serving I recommend 1/3 cup, and for a large serving, 1/2 cup.
I know, I know. This is a pointless step that you would rather just skip, but cooking is almost always more fun with a little preperation.
Is it actually important to wash rice? Yes, please do not skip this step. How much? Until the water is mostly clear (about three times, it may never get clear).
Pretty self-explanatory, but the temperature of the liquids (within reason) is not very important, so do not worry about that.
Start off with higher heat, and when you get up to the target slow bubble reduce the heat to maintain that temperature. This step will take a variable amount of time depending on your type of rice and elevation, but in general about 20 minutes. Stir occasionally, and optionally cover with a lid for the first 10 minutes to increase efficiency (just be careful that the milk does not boil over).
After the rice is starting to thicken up you can add the banana. While the heat is still on, mash the banana into the rice till homogeneous. The goal is not necessarily to crush the rice, so do not worry about that. After adding the banana you can optionally add any spices or sugar you want.
You did it!
For the ingredient amounts stated, without the optional sugar.
I just enjoy eating rice porridge. There is really no great backstory, just that one day I did not have any oats and decided to try modifying a vaguely-remembered rice pudding recipe to create porridge. I hope you enjoy :)