For the crust: In a food processor, place the flour, salt, and sugar and process until combined. Add the butter (distribute equally on the sides) and process until the mixture resembles coarse meal, about 15 seconds. Pour in the 1/4 cup of water, distributing equally in circles, and process again until dough just holds your fingertips together when pinched. If necessary, add one or two tablespoons of water to the dough.
Turn the dough onto your work surface and gather into a ball. Flatten into a disk, cover with plastic wrap, and refrigerate for about 60 minutes before using. This will chill the butter and relax the gluten in the flour.
After the dough has chilled, place on a lightly floured surface, roll out the dough and cut into 12 - 4 inch (10 cm) rounds (to prevent the pastry from sticking to the counter and to ensure uniform thickness, keep lifting up and turning the pastry a quarter turn as you roll -- always roll from the center of the pastry outwards). Gently place the rounds into a 12-cup muffin tin. Cover with plastic wrap and place in the refrigerator for approximately 30 minutes to firm the dough.
For the filling: Preheat oven to 375º F (190º C). In the electric mixer, beat the butter and sugar until creamy and smooth. Beat in the eggs, one at a time, and then the vanilla extract. Stir in the cream. Place half of a dried prune in the bottom of each tart shell and a spoonful of the cashew nut and coconut mixture. Then, fill the unbaked tart shells with the filling (2 to 3 tablespoons per shell). Bake for about 15 - 20 minutes or until the pastry has nicely browned and the filling is puffed and set. Remove from oven and place on a wire rack to cool. Serve at room temperature or chilled.