Directions

1. Make the sauce  You use either a regular blender or a stick blender.
2. In the blender Put the ingredients into the jar in the order that they’re given. Whip, starting on low speed and quickly ramping up to high, until the sauce thickens and is very smooth, 2–4 minutes.
3. With an immersion blender  Put the ingredients into a container just wider than the blending head and with high sides. Whip on high speed keeping the blending head pressed against the bottom of the container for the first couple of minutes. As the sauce becomes smooth and a little thicker, you can lift the head from the bottom. Process until the sauce thickens and is very smooth, 3–5 minutes. Set aside.

4. Cook the salmon  Rinse the salmon and pat it dry. Sprinkle ¼ teaspoon of the salt over the fish. Set a cooling rack over a rimmed plate. Set both aside.

5. Set a heavy pan (wide enough to accommodate the fish) over medium-high heat. Add the water, spices, celery, lemon, onion, and remaining salt; cover the pan and bring the water to a boil. Take the pan off the heat for about 5 minutes. Reduce the heat to medium-low and return the pan to the burner. The water should be hot, almost ready to boil, but not bubbling (about 195° F).
6. Use a spatula to slip the fish into the water; cook until its almost done (about 125° F in the thickest part of the fillet). Use the spatula to transfer the fish to the cooling rack to drain for a moment. Cooking time varies with the thickness of the fillet.
7. Serve  Top the salmon with ample sauce and garnish with chives.