Combine Dry Ingredients: In a large mixing bowl, whisk together the flour, sugar, and salt.

Incorporate Butter: Add the cold butter, using a pastry cutter or your fingers to work it into the flour mixture until it resembles coarse crumbs with pea-sized butter pieces. (For a food processor, pulse the dry ingredients with butter until crumbly.)

Form the Dough: Gradually mix in the cold water, 1 tablespoon at a time, until the dough comes together. (In a food processor, add water and pulse until the dough forms a ball.)

Chill the Dough: Shape the dough into a thick disk, wrap it in plastic wrap, and refrigerate for at least 1 hour or up to 1 week.

Roll and Cut: On a floured surface, roll out the dough to about ⅛-inch thickness. Use a 3.5–4-inch round cutter or cup to cut out circles.

Shape the Shells: Gently press each round into a 12-cup muffin pan, ensuring the dough lines the bottom and sides without holes. If needed, patch any holes by pressing the dough together. Freeze the pan for 10–15 minutes to help the crust hold its shape during baking.

Preheat the Oven: Set the oven to 350°F (175°C).

Mix Filling Ingredients: In a large bowl, whisk together the brown sugar, corn syrup, melted butter, eggs, vinegar (if using), and vanilla until smooth.

Assemble the Tarts: Evenly pour the filling into the prepared tart shells, filling each about two-thirds full. Add raisins or pecans, if desired.

Bake the Tarts: Place the muffin pan in the preheated oven and bake for 20–25 minutes, or until the crust is golden and the filling is set but still slightly wobbly in the center.

Cool: Allow the tarts to cool in the pan for 10 minutes, then transfer them to a wire rack to cool completely.