Heat the oven to broil. Mash together the butter, sugar, pistachios and flour and chill for 1 hour. Cut a cross from the top about three-quarters of the way down into the figs. Divide chilled filling into as many balls as you have figs, and poke the filling into the openings of each fig. Broil until the nut mixture is golden and the figs hot, 8 to 10 minutes. Serve with whipped cream or creme fraiche.