Delicious warm or at room temperature, this poached salmon only takes 30 minutes and can be made ahead so it's a hit with savvy home entertainers. Try it with Miso Aioli or Gingery Tomato-Basil Sauce.
Generously season fish with salt and pepper. Transfer to a straight-sided skillet, saucepan, or shallow pot slightly larger than fish, skin-side down. Scatter leek, celery, bay leaf, lemon rounds, and peppercorns around fish. Add wine and enough water to submerge fish by 1 inch. Attach a deep-fry thermometer to skillet.
Heat over medium until liquid reaches 150 degrees. Reduce heat to low to maintain temperature (remove skillet from heat briefly if it climbs above 150 degrees). Cook until fish turns opaque and is just cooked through, 6 to 10 minutes, depending on thickness. With a fish spatula, transfer to a plate, skin-side up. Let cool slightly; remove skin. Serve warm, room temperature, or chilled, with lemon wedges.
Use skin-on fillets if you can: The fat adds flavor, and laying them in the pot skin-side down prevents the pieces from sticking.