Stir together the goat cheese, 2 tablespoons of the pistachios, and the chives in a small bowl until smooth.
Season with pepper.
Arrange the dates, cut side up, on a platter.
Fit a pastry bag with a large round tip, and fill it with the goat cheese mixture.
Pipe the mixture onto each date half to cover.
(Alternatively, pipe the goat cheese mixture using a resealable plastic bag with 1 inch cut from one corner, or simply spread the mixture on the dates with a butter knife.)
Garnish the dates with the remaining tablespoon pistachios and more chives.