Prepare the rice noodles in accordance with package instructions, ensuring the noodle still has a bit of bite to it. Once cooked and strained allow the noodle to cool by rinsing it with cold water.
While the noodle is cooking roughly chop the onions, place in a blender with the paprika and blend to form the base gravy paste.
In a deep non-stick frypan or small non-stick pot; heat the oil on high. It is important that when the blended onions hit the pot there is a rapid sizzling sound. (See note 1)
When the oil is hot add the base gravy paste and keep mixing to ensure the paste doesn't catch onto the pot. The base gravy onion paste need to keep frying on high heat until the oil and gravy move as one and the raw onion smell is gone. (See note 2)
While the onion is frying (I like to multi-task but feel free to do this step before you begin if you wish) dice the chicken thighs into small bite size pieces, coat with tumeric, a bit of salt and allow to sit for 5 - 10 minutes.
When the raw onion smell is gone add the coated chicken pieces and cook on medium heat until the chicken is cooked through.
When cooked through season with salt to taste, take off stove and allow to cool. (Note 3)
Once the noodles and gravy have cooled down, in a large mixing bowl, place the rice noodles, chicken gravy, fish sauce (to taste), lemon (to taste), roasted dahl powder, red onion and coriander. Then get your hands in there and toss the noodles to get a good even coating on them.
The noodle salad shouldn't be overly dry so, if it is, the ratio of roasted dahl powder to gravy is a slightly off. To restore the salad to the right moisture level add more curry gravy / fish sauce / lemon.
Once happy with the balance of the dish transfer into individual serving dishes and place a slice of lemon incase someone prefers it extra zesty. (Note 4)
Note 1: The onion paste needs to literally fry, like shallow fry in the oil. A failure to ensure high heat when the onion hits the pan means that the onion gravy will struggle to become sweet and caramelized.
Note 2: The onion paste needs to be suspended and somewhat swimming in the oil. If the ratio of oil to onion is a bit off feel free to add in more oil to the pot to encourage full caramelization.
Note 3: You can keep the curry gravy in the fridge for making the noodle salad later on in the week. To do so just lightly zap the required portion of the gravy in the microwave until lukewarm to use.
Note 4: It is best to eat this dish soon after it has been made. Leaving it out to sit for a while may cause the noodle to dry up and not be optimum.