Make the pastry crust by whisking all-purpose flour, sugar, and salt together in a bowl. Cut in cold unsalted butter with a pastry blender until pea-sized crumbs form, then stir in ice water one tablespoon at a time until the dough comes together.
Shape into a flat disk, wrap in plastic, and chill in the refrigerator for 30 minutes. Preheat the oven to 375°F (190°C) and lightly grease a standard 12-cup muffin tin.
Roll out the chilled dough on a lightly floured surface to 1/8-inch thickness. Cut out 4-inch rounds using a cookie cutter and press each round into the bottom and up the sides of the muffin cups, then divide raisins among the pastry bottoms.
Melt unsalted butter in a medium saucepan over medium-low heat. Stir in dark brown sugar, pure maple syrup, and cornstarch, whisking constantly until smooth and simmering.
Remove the saucepan from the heat and whisk in heavy cream, vanilla extract, and salt until completely blended and silky.
Spoon the warm brown sugar filling into each prepared tart shell, filling each about two-thirds full.
Bake at 375°F (190°C) for 16 to 18 minutes until the pastry edges are golden brown and the filling is bubbling actively.
Let the tarts cool in the pan for 15 minutes to allow the gooey centers to set, then gently run a thin spatula around the edges and transfer to a wire rack to cool completely.
