First make the paste with a pestle and mortar. Pound the salt, lemongrass, galangal, and turmeric into a smooth paste. Then add each ingredient as it's listed, in order, one at a time, pounding each until smooth.
Add the dried mushrooms to a spice mill or blender and pulse until fine. The texture is up to you – a little chunky or fine as a powder. You don't want any large pieces.Alternatively, if you don't have a blender, soak the mushrooms in warm water until soft. Then drain and finely chop them. Add the oil and 2 tablespoons of the coconut milk to a saucepan, along with the paste from step one. Heat on medium low, stirring frequently, for a few minutes until it no longer smells like raw onion and garlic.
Add the remaining coconut milk, soy sauce, palm sugar, and mushrooms. Give everything a stir and continue to cook for 5-10 minutes. You should see some vibrant red oil rise to the top. Turn off the heat and stir in the peanuts.
Leave to cool to room temperature and serve with sliced baguette, rice crackers, and/or crudités.