Put the sugar, 2 cups water, and cardamom into a saucepan, and bring to a boil. Boil until thick syrup forms a thread when pinched between thumb and forefinger, about 15 minutes. Let the mixture cool slightly.
Melt the butter in a large skillet and add the chickpea flour. Cook over medium-low heat until it turns a deep golden brown, about 8 minutes. Stir this mixture into the syrup along with half the pistachios and press into the baking pan. Sprinkle the top with the rest of the pistachios and let set for about 1 hour. Cut into squares and serve.