• Preheat the oven to 400 degrees fahrenheit.

Crust

• In a medium bowl stir the flour and salt together. Use a pastry cutter to cut in the shortening until it is pea-sized.
• Add in the water one tablespoon at a time, tossing with a fork. Add water and mix until all the flour is moistened and it comes together in a shaggy dough. Use your hands to knead the dough just until it comes together into a ball, being careful not to overknead. This will lead to a tough dough.
• Roll the dough out on a lightly floured surface, turning and flouring the dough as needed until the dough is about ¼ inch thick.
• Use a 3-inch circle cutter to cut out 12 circles of dough. If necessary, gently press the scraps of dough together and let it rest for 5 minutes before rolling out again to cut out additional circles.
• Press the circles of dough into a lightly greased muffin tin, so each muffin well looks like an individual tart shell. Set in the fridge while you prepare the filling.

Filling

• Add the butter to a large measuring cup and heat in the microwave for 15-20 seconds, until fully melted.
• Whisk in the brown sugar, corn syrup, egg, and vanilla. Pour the filling evenly into the chilled dough.
• Bake for 15-18 minutes, until the filling is set. Let cool completely before serving.