In a medium bowl combine melted butter, brown sugar, maple syrup, eggs, vinegar and salt and whisk until combined. Add raisins and chopped walnuts.
Roll out the pastry to a ⅓ cm/1/8" thickness and cut out rounds with a 10 cm/4" pastry cutter or use a glass. (My glass was 9 cm/3.5" in diameter) Line muffin tin cups with pastry rounds. Fill the muffin cups with the maple/nut mixture until ⅔ full.
Bake for 20-25 minutes until the custard is set and the pastry is golden. Run a knife around the edges of the tarts as soon as you remove them from the oven to release them from the tin.