Preheat the oven to 350 degrees F.
Heat a large non-stick saute pan until hot. While the pan is heating, season the salmon fillets with the salt and white pepper. Pour the oil into the pan and warm oil for 15 seconds. Place the salmon fillets, flesh side down, into the saute pan. Using a low flame, saute the fish for about 2 1/2 minutes. Place the pan in the oven and roast for 6 to 7 minutes. The salmon should be medium rare. When serving, turn the salmon fillets over to expose the nicely browned side.
Place spinach mixture in a mold on a plate. Place salmon on the top. Pour the sauce around the fish. Garnish with minced lemongrass and lime leaves.
Using a low flame, heat a stainless steel saucepan. Warm the oil in the pan for 15 seconds. Add the minced shallots and sweat for 30 seconds. Next, add 2 cups of the white corn kernels. Add the coconut milk, reserved corn cobs, bruised lemon grass stalks, galangal, and 2 bruised or crinkled kaffir lime leaves, and white pepper. Simmer the mixture for about 7 to 10 minutes, not letting it reduce very much.
Remove from the heat and add the nam pla. Let the mixture rest to absorb all the aromatic flavors for 30 minutes. Take the corncobs, lemongrass, galangal, and kaffir lime leaves out of the saucepan and throw them away. Puree the mixture until smooth.
Heat sauce in a stainless pan. Add the remaining corn to the pan.
Bring the water to a boil in a large pot. When the water comes to a boil, add salt. In a large bowl add some ice and water to create a water bath.
Add the spinach to the boiling water and cook for 1 minute. Drain the spinach. Place in the ice bath to cool. Drain spinach and squeeze very dry.
Add butter to a saute pan and heat. Add shallots and cook for 1 minute. Add mushrooms and saute until the release their liquid, about 5 minutes. Add spinach and saute until heated through. Season with salt and pepper.