In large bowl, whisk flour with salt. Cut in butter with pastry blender or rub through fingertips until mixture resembles coarse meal. In small bowl, whisk egg yolk with vinegar and 3 tbsp (45 mL) water. Stir into the flour mixture until dough just comes together. Do not overwork. Stir in 1 tbsp (15 mL) more water if needed. Form dough into a flattened disk, wrap in plastic wrap and refrigerate at least 1 hr.
Roll dough on lightly floured work surface. Using 4-in. (10-cm) round cutter, cut into 12 rounds, rerolling scraps as needed. Fit each round into standard muffin tins. Chill 10 min. in freezer.
Preheat oven to 400°F (200°C). Set rack to lowest position. To make filling, in bowl, whisk corn syrup, brown sugar, eggs, melted butter, vanilla, vinegar and salt until blended. Spoon filling into pastry shells ¾ full. Place muffin tin on baking sheet lined with parchment or foil to catch drips.
Bake 18 to 20 min. or until filling is puffed and bubbly and pastry is golden brown. Transfer muffin tin to a wire rack. Let stand 5 min. Run paring knife around tarts to loosen. Carefully slide metal spatula under tarts to remove. Transfer tarts to rack to cool completely.
Chilling time: 60 min.