Pick enough tarragon leaves to measure 1/2 cup (do not pack). Chop enough chives to measure 1/3 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.
In a deep 10-inch skillet bring wine and water to a simmer, covered. Cut salmon into 6 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.
Cut potatoes lengthwise into 1/8-inch-thick slices. In a steamer set over boiling water steam potatoes until just tender, 4 to 5 minutes. Spoon sauce onto 6 plates and arrange some potatoes in a circle, overlapping slightly, on top of sauce . Season potatoes with salt and arrange salmon on top of potatoes. Garnish salmon with peas.
