Line a 3-cup mold or 3- to 4-cup bowl with plastic wrap; set aside.
In a medium bowl stir together salmon and the 4 ounces cream cheese. Spread evenly in the bottom of the prepared mold. Spread pesto over salmon mixture. In a medium bowl stir together the 8 ounces cream cheese, the butter, 2 tablespoons chives, and pepper. Drop by spoonfuls over pesto; gently spread over pesto. Cover and chill for at least 6 hours or up to 24 hours.
To serve, uncover and invert mold onto a serving platter; remove plastic wrap. Let stand at room temperature for 15 minutes. If desired, garnish with additional chives. Serve with assorted crackers.
Makes about 2-1/2 cups spread (twenty 2-tablespoon servings).