Beat 1 1/2 cups of the butter in the bowl of a stand mixer on high speed until soft. Add sour cream, lemon zest, and lemon juice, and beat until incorporated. Set aside.
Cut salmon into small pieces, and set aside.
Melt remaining 2 tablespoons butter in a skillet over medium. Add shallots, and cook, stirring often, until fragrant, about 3 minutes. Stir in pastis, and cook until slightly reduced, about 2 minutes. Remove from heat, and let cool 10 minutes; stir into butter mixture.
Add salmon, and beat on high speed 1 minute. Gently stir in chives, and chill until ready to serve. Serve with Pickled Shallots and Seasoned Saltine Crackers.
The Walrus and the Carpenter, and others, Seattle