Preheat the oven to 350 degrees F and grease a mini muffin pan.
Beat the 1/2 cup unsalted butter, softenedand 3 ounces cream cheese, softened in the bowl of a stand mixer until smooth.
Add the 1 cup all-purpose flour and mix just until a dough forms.
Divide the dough into 24 equal balls and drop one into each cup of the pan.
Lay a piece of plastic wrap over the balls and press the dough evenly across the bottom and up the sides of each cup, using the blunt end of a wooden spoon anywhere the dough resists.
Spread the 1 cup chopped pecans on a baking sheet pan and toast at 350 degrees F for 6 to 8 minutes, until fragrant. Set them aside to cool for a few minutes.
Stir the toasted pecans, 1/2 cup light brown sugar, packed, 1/4 cup light or dark corn syrup, 1 large egg, 1 tablespoon unsalted butter, melted, 1 teaspoon vanilla extract, and 1/8 teaspoon salt together in a large mixing bowl.
Spoon the filling into the shells, filling each one only to the top edge of the crust. Filling above the rim runs over onto the pan instead of staying in the shell.
Bake for 25 to 30 minutes, until the filling has set.
Cool in the pan for 10-15 minutes
Run the tip of a thin knife around each tassie, lift it straight up onto a cooling rack, and let them cool completely before serving.