- WHIRL flour and salt in a food processor. Add butter and lard. Pulse until coarse crumbs form. Whisk yolk, vinegar and ice water in a small bowl. With motor running, pour through feed tube while pulsing until just combined. Wrap with plastic wrap and press into a disc. Refrigerate for 1 hour.
- POSITION rack in bottom of oven. Preheat oven to 450F.
- WHISK sugar, corn syrup, maple syrup, eggs, butter, vanilla, vinegar and salt in a bowl until smooth.
- ROLL out dough on a lightly floured surface to ⅛-in. thickness. Cut into 12 rounds using a 4 ½-in. round cookie cutter, re-rolling scraps. Gently press rounds into a 12-cup muffin pan. Press sides to adhere. Refrigerate for 20 min. Spoon 2 tbsp filling into each pastry.
- BAKE for 8 min. Reduce heat to 400F and open oven slightly for 10 sec. Bake until filling is puffed and pastry is golden, about 7 more min. Let stand on rack for 3 min. Run a small knife around the edges of tarts and transfer to rack to cool completely.
Chocolatey Butter Tarts: Top each tart with 2 tsp coarsely chopped dark chocolate just before baking.
Boozy Butter Tarts: Stir 1 tbsp whisky into filling just before pouring into pastry. Top each tart with 1 tsp chopped dried cranberries.
Pecan Butter Tarts: Top each tart with 1 tsp chopped pecans before baking.
Weekend baking: Classic butter tarts