First, make your dough.

Whisk together the flour, sugar, and salt in a large bowl or the bowl of your food processor. Add in the chopped pieces of cold butter and cold shortening.

Blend together with your hands or pulse with your processor until you have coarse crumbs.

Mix together the water and vinegar in a small bowl. When ready, slowly drizzle it over the dough, a tablespoon or so at a time, gently stirring the mixture with a fork or pulsing with your processor, until fully incorporated (you may not use all of the water).

It might seem a bit too wet at this point, but it will dry up while it sits in the fridge. Form the dough gently into 2 loose balls, wrap tightly in plastic wrap, and chill in the fridge for a minimum of 3 hours or as long as overnight.

Make your filling when you are almost ready to use your dough.

When you're ready to bake, liberally butter your muffin tins.

This recipe makes about 30-36 tarts.

Preheat your oven to 400 degrees F.

Lightly flour a work surface, and take one of your balls of dough and roll it out to about ¼-inch thick.

Cut out circles that are a bit larger than the circumference of your tins, so that there is enough crust to hold in the filling, and gently place each circle in the tins, re-rolling your dough as you go.

Drop 3-4 raisins in the bottom of each tart before adding in the filling.

Whisk together your dark brown sugar, corn syrup, melted butter, and vanilla. Drop 2-3 teaspoons of filling (it will bubble during baking so don't overfill ) then sprinkle with a touch of sea salt.

Bake for 12-15 minutes, until lightly golden and mostly set.

Allow to cool completely before removing the tarts from the pan. I used a dull paring knife to cut around any hardened caramel and then popping each tart out.

These will keep well at room temperature for up to 3 days, or frozen for up to 3 months.