Wash rice and mung bean (if using) and drain, add to the pressure cooker.
Scrub fish bones with salt and rinse under cold water. Add to the pressure cooker.
Peel and slice ginger into thin slices. Peel and cut shallot in half. Place in the pressure cooker. Add water and 1 teaspoon salt to the pressure cooker too. Cook on high pressure for 12 minutes (you can also select Porridge mode if using Instant Pot).
While the congee is cooked in the pressure cooker, slice fish fillet on the diagonal into 1/2 in thick pieces. Season with a pinch of salt and pepper, set aside.
Once the pressure cooking is over and the pressure has been naturally released, remove and discard the fish bones. If using an Instant Pot, switch to Sauté mode, add fish fillet slices. Cook for a couple minutes or until fish is fully cooked.
Check consistency, if it's too thick, add some more water. If it's too thin, simmer a little more. Add 1 tablespoon of fish sauce and adjust seasoning to your liking.
Transfer congee to serving bowl and add toppings and herbs of your choice.