Preheat oven to 350 degrees.
Whisk all the ingredients for the marinade together in a small bowl and set aside.
Take 2 large pieces of parchment paper, and fold each in half lengthwise. Place each fillet at the bottom end of each piece of parchment paper.
Place the pieces on a large baking sheet, with sides.
Pour the marinade equally over each piece of fish and fold the top of the parchment paper over the fillet, folding up the sides to seal the marinade in. It should now look like you have two square little packets.
Place the tray in the oven and bake for 25 minutes.
While the fish is baking, mix all the ingredients for the peanut butter sauce, it may look a bit thick, and that is okay as you will add more liquid later. Set aside until the fish finishes.
Once the fish is done, carefully open the packages. You want to make sure that marinade doesn't seep out everywhere, as you want to use it again!
Transfer the fish to a plate, and stir the leftover marinade liquids into the peanut butter sauce.
Pour the peanut butter sauce over the fish, garnish with cilantro and chopped peanuts, and devour!