Sift together the flour, sugar and salt. Cut in the shortening with a fork or pastry cutter or in a food processor to form a crumbly dough.
Sift together 4 tbsp of the ice water and vinegar, then drizzle a third of it over the flour. Gently mix to moisten, drizzle in another third of the liquid, and mix to moisten. Repeat with the remaining mixture until the dough forms a soft ball when pressed together. If it hasn't come together yet, sprinkle it with another tbsp (or more) of ice water until the dough can be gathered into a ball. Wrap it in plastic wrap or sandwich between waxed paper and refrigerate for an hour.
When you are ready to roll out the crust, tear off a 14-inch piece of waxed paper or baking parchment and lightly sprinkle it with flour. Flatten the dough into a disk and place in the center of the paper. Using a lightly floured rolling pin, in even, long strokes, roll out the dough into a circle about 12 inches in diameter. Occasionally rotate the dough while you're rolling to help form an even circle.
To transfer the dough to a pie plate, slide your hand underneath the center of the paper and quickly flip it onto the plate. Peel off the paper and gently press the dough into the plate. If necessary, trim any overhanging dough edges with a sharp knife, leaving about 1 1/2 inches of dough for the crimped edge. Crimp the edges as desired.
For the caramel, in a saucepan, mix together the sugars and the maple syrup. Heat over medium heat, stirring often with a whisk. Once small bubbles start forming rapidly, stir pretty constantly for 10 minutes. The mixture should become thick and syrupy. It shouldn't be boiling too fiercely. If big bubbles start climbing the walls of the pan then lower the heat a bit.
Add the margarine and stir to melt. Turn off the heat, transfer the mixture to a mixing bowl, and let it cool for a bit. In the meantime prepare the rest of the filling.
Crumble the tofu into a blender or food processor, along with the milk, cornstarch, and salt. Puree until completely smooth, scraping down the sides of the blender to make sure you get everything.
Preheat the oven to 350 degrees. Check and see that the sugar mixture has cooled sufficiently; it's okay if it is a bit warm, just not boiling hot. Add the tofu mixture and the vanilla extract to the sugar mixture and mix well. Fold in the pecans.
Transfer the filling to the prepared pie crust and bake for 40 minutes. When done, the pie is going to be somewhat jiggly, but it should appear to be set. Let cool, slice, and serve!