Put flour and salt in food processor and pulse.
Cube butter, then add to flour in processor bowl and pulse until it resembles coarse meal.
Add vinegar to milk. Add all at once to flour mixture. Pulse until it just forms a ball.
Remove and divide into two balls. Place on waxed paper or plastic wrap, flatten gently into a disc, top with another layer of wrap, fold over and refrigerate if not using right away.
Roll out and cut to fit your tart tins. Press gently into tins, smoothing out any creases. Prick several times with the tines of a fork.
Rinse the raisins with hot water a couple of times. After draining the last time, squeeze them with your hands to remove excess water.
Measure the brown sugar, maple syrup and butter into a medium bowl. Add the raisins and stir.
Add the eggs and vanilla and stir thoroughly to combine. Stir in the chopped pecans or walnuts, if using.
Carefully spoon into 24 three-inch pastry-lined tart shells, filling 2/3 full.
Bake in 350°F. degree oven for 22 – 24 minutes or until pastry is golden brown. Remove and let cool on a wire rack.