For the filling: In the top of a double boiler, whisk together the butter, sugar, eggs, and passion fruit juice until the mixture is thick and will hold a line, about 12 minutes. Transfer the double-boiler insert to a larger bowl filled with ice and cold water, and stir occasionally until cool. The mixture will be quite thick.
For the crust: In a large bowl, combine 2 cups of the flour, the salt, lard, and butter and rub together with the tips of your fingertips until the mixture resembles small peas. Add the remaining 1/4 cup flour and bring together into a rough mass. Add the ice water, 1 tablespoon at a time and press into the mixture with a fork or your fingertips just until the mixture adheres into a dough. You may not need all the ice water. Press the dough into a ball and refrigerate for 2 hours.
To assemble the tarts: Roll the dough out to 1/8-inch thick and, using a small plate or a cardboard template, cut the dough into six 4 1/2-inch diameter rounds. Transfer the rounds to 2 baking sheets, prick all over with a fork, and freeze for 20 minutes. Preheat the oven to 425.
Bake the tart bases for 12 to 15 minutes, until slightly golden. Using a large heavy spatula, transfer them to a rack (they crumble easily) and, when cool, spread with a nice thick layer of the passionfruit curd almost out to the edges of the pastry. Scatter the pistachio nuts around the very edges of the tarts and serve.
Unsweetened passion fruit juice, which is very sour, is sometimes available frozen. Or, in season scoop out and, if desired (it is not necessary), strain the pulp of 1 passion fruit for each 2 tablespoons juice required. If you use regular storebought passion fruit juice, which has been sweetened, add 2 tablespoons of lemon juice for each 1/2 cup of the juice.
c.1997, M.S. Milliken & S. Feniger, all rights reserved