Make the red curry paste. Combine all the ingredients for the red curry paste into a blender and blend until everything is broken down. It should look almost like an orange smoothie. Set aside.
Bring 6 cups of water to a boil in a soup pot. Once boiling, dump in the salmon, mushrooms, red bell peppers, and Thai eggplant and cook for 10 seconds. Boiling the salmon and vegetables will produce a cleaner flavor in the finished curry. Take everything out and set aside.
Add a tablespoon of oil to a large pan. Add in the onions and cook for about a minute.
Add in the red curry paste and coconut milk. Reduce the liquid for 3-5 minutes until it starts boiling.
Add in the salmon and cook for 2-3 minutes.
Add in the mushrooms, red bell peppers, eggplant, salt, coconut sugar, and fish sauce. Stir and cook for another 2-3 minutes until the salmon is cooked through.
Lastly, add in the Thai basil leaves and stir. Turn off the heat.
Serve over a bed of rice with cilantro and mint for garnish.