Make the sauce: Pick enough tarragon leaves to measure 1 cup (do not pack). Chop enough chives to measure 2/3 cup. Coarsely chop shallot. In a food processor puree tarragon, chives, and shallot with remaining sauce ingredients until smooth and season with salt and pepper. (Sauce may be made 1 day ahead and chilled, covered. Bring sauce to cool room temperature before serving.)
Make the salmon: Bring the wine and water to a simmer in a large, deep skillet with a tight-fitting lid. Cut salmon into 12 pieces and season with salt and pepper. Submerge 3 salmon pieces, skin sides down, in simmering liquid (add hot water, if necessary, to just cover salmon) and poach at a bare simmer, covered, 8 minutes, or until just cooked through. Transfer cooked salmon with a slotted spatula to a platter to cool and poach remaining salmon in same manner. When salmon is cool enough to handle, peel off skin and if desired with a sharp knife scrape off any dark meat. Salmon may be cooked 1 day ahead and chilled, covered. Bring salmon to cool room temperature before serving.
When ready to serve, spoon sauce onto a large serving platter or divide among 12 plates and garnish with peas.