Slice fish into 1/2 - 3/4-inch thick pieces. You may need to slice on an angle to have wide pieces.
Peel galangal, slice and finely chop. If possible, use a pestle and mortal to crush into finer pieces (about 3 tablespoons).
In a mixing bowl, add fish and all ingredients in the first group and mix well. Refrigerate and marinate for at least 30 minutes or more for a tastier result.
Cut scallions into 2-inch long pieces, keep the white and green parts separated. Also cut dills into 2-inch long pieces.
Whisk together all ingredients for the dipping sauce, taste and adjust to your liking.
Prepare vermicelli noodles according to package instructions.
After fish has been marinated, remove from the refrigerator. Place a pan over medium high heat, add cooking oil, put fish in a single layer and sear and both sides to cook. You may need to sear in several batches. Another option is to broil fish on high for 8-10 minutes. Transfer to a clean plate.
Wipe the pan clean, place over medium - medium high heat. Add oil and then add the white part of scallions. Sauté for about a minute until color starts to develop, then add the green part. Sauté for 20-30 seconds and then add dill. Give everything a quick mix to combine and wilt the dill.
Add fish slices to the pan, stir to mix with scallions and dills. Be careful to not break the fish slices.
Transfer everything to a preheated cast iron fajita plate or a regular plate and serve immediately with noodles, roasted peanuts and dipping sauce.