For the pastry, combine the flour and salt in a large bowl. Cut the butter and shortening into small pats and quickly rub and snap it into the flour mixture until it resembles very coarse sand with some hunks of butter and shortening that are about the size of a pea. In a small bowl, combine the ice water and vinegar and pour it over the flour and fat mixture. Using a wooden spoon, gently mix until a shaggy dough forms. Dump the dough onto a work surface and give it two or three kneads to bring the dough together. Transfer the dough to a piece of cling film and wrap and press the dough into a 2.5 centimeter thick disk. Pop this in the fridge for 45 minutes or so to allow the flour to hydrate and re-chill the fat.
Meanwhile, mix up the filling by whisking together the brown sugar, corn syrup, eggs, melted butter, vanilla, vinegar, and salt in a large glass measuring cup. Set aside.
When the dough has chilled, remove it from the fridge and set it out on a lightly floured work surface. Roll the dough to about six millimeters thick and cut out as many circles as possible with an 11 centimeter round cutter. If you don’t get 16 rounds, simply gather the rest of the dough, reroll it to six millimeters thick, and cut out more circles. Gently press the circles into a muffin tin, rumpling the sides lightly so that they are a little wavy and loose to give them that homemade look (I have to use two tins to fit all 16 tarts). Pop the lined muffin tins into the fridge for 20 minutes to rechill the dough and preheat your oven to 450F.
Once chilled, toss a few chopped pecans or raising, if using, in each tart shell and top with about two tablespoons of that lovely filling. Bake the tarts for eight minutes then reduce the heat of your oven to 400F. Open your oven door for about five to ten seconds to quickly bring the heat down then close the oven and continue to bake for 10 to 12 minutes or until the filling is puffy and the pastry is golden.
Allow the tarts to cool for ten minutes in the muffin tin then carefully remove to a cooling rack to cool completely.