Makes enough dough for four 10-inch tarts

Mix flour and salt together in a large bowl.  Add butter and cut it into the flour until the mixture looks like coarse crumbs.  Break up the shortening and cut it in until mixture has small clumps and curds.  Add ice water, stirring with a spoon to incorporate.  Turn dough out onto a work surface and fold it over on itself a few times.  Wrap dough in plastic and refrigerate at least 2 hours.