You'll want to bake these right after filling, so get your oven preheating to 400 degrees F.
Melt butter and allow to cool slightly.
In medium size bowl, whisk together eggs, corn syrup, brown sugar, vanilla extract and vinegar. Add melted butter and raisins.
Using a spoon or small ladle to help, put filling into prepared pie shells. Fill up the shells only half way - they will expand quite a lot in the oven and will overflow if filled all the way. Once filled put in the preheated oven to bake.
Bake tarts for about 25 minutes, rotating half-way through. Tarts should be golden brown and slightly firm to the touch. Pull from oven.
Right when the tarts come out of the oven, use a thin-bladed knife or small offset spatula, and run edge around outside of baked tarts, to release the sides of the tarts from the pan. Allow tarts to rest in tins for about 10 minutes.
Once the tarts have cooled slightly, use a knife or offset spatula to help you ease the tarts out of the muffin tin. Place tarts on a rack to cool a bit more, then serve.