Instructions

1. Make the dough: In a large bowl, sift together the flour and salt. Using a pastry cutter or two knives, work the vegetable shortening into the flour mixture until it resembles coarse meal, then set aside. In a medium bowl, whisk together the egg, vinegar, and 1 cup of cold water, then drizzle the liquids into the flour mixture while stirring with a fork just until a shaggy dough begins to form. Lightly flour a clean work surface, then turn the dough out onto it. Give the dough several quick kneads to smooth, then shape into a 1-inch-thick disk. Wrap tightly in plastic and refrigerate for at least 1 hour or up to 2 days.
2. Meanwhile, make the filling: To a medium pot, add the raisins and enough cold water to cover by 1 inch. Bring to a boil over high heat, then drain, discarding the cooking liquid. Transfer the raisins to a medium bowl, then add the brown sugar, maple syrup, corn syrup, and butter and stir until the butter melts and the mixture is combined. Set aside to cool slightly, 3–4 minutes. In a small bowl, beat 1 egg well, then fold it into the raisin mixture. Repeat with remaining 3 eggs. Stir in the vanilla and set the filling aside at room temperature. (The raisins will sink to the bottom and need to be stirred up again when you fill the tarts.)
3. Position a rack in the center of the oven and preheat to 425°F. Meanwhile, retrieve the dough from the fridge and unwrap. Lightly flour a clean work surface and a rolling pin, then roll out the dough to an even ¼-inch-thick sheet. Using a 4-inch round cookie cutter, cut 28 circles from the dough, gathering the scraps into a ball and rerolling as needed. Press the rounds into standard-size muffin tins, then fill each with 2 tablespoons of filling.
4. Bake until the crusts are lightly golden and the filling is crackly and dry on the surface and barely set, 12–15 minutes. Cool the tarts completely, then use a thin, offset spatula or butter knife to lift them carefully from the tins. Serve at room temperature.