Scoop the thick coconut cream out of the 2 cans of full fat coconut milk. Heat it in a large Dutch oven; when it starts to separate, add the curry paste. Fry the paste, stirring, on medium heat, until it separates.

Add 1/3 of the onions and the palm sugar. Stir. Add the rest of the coconut milk, including the can of light milk. Add 2 cups of chicken stock, the tomatoes, the kaffir lime leaves and 1/4 cup of fish sauce. Bring to a simmer.

In the meantime, heat the coconut oil in a large nonstick skillet. Add the rest of the onions and caramelize on medium-high heat. Add a pinch of salt at the beginning. Cook until well-browned--reduce the heat if they start to stick and scorch.

Check on your broth. If you want more of a sauce, it may be just right, but if you want it brothier, add more chicken stock until it is where you want it. Taste for more palm sugar or fish sauce.

About 10 minutes before serving, add the fish chunks and let them slowly simmer (do not boil) until they are cooked through.

To serve place a handful of noodles in a bowl, ladle broth over it, and then garnish with toasted coconut flakes, bean sprouts, cucumber slices and caramelized onions. Serve with Sirracha sauce and fish sauce for adjusting at the table to preference.