Step 1: Prepare the shortbread base. In a medium bowl, cream together the softened butter, powdered sugar, and ½ teaspoon vanilla extract until light and fluffy. Add the all-purpose flour and a pinch of salt, mixing until just combined and a soft dough forms. Do not overmix.
Step 2: Chill the dough. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes. This helps prevent spreading during baking.
Step 3: Preheat oven and prepare muffin tins. Preheat your oven to 350°F (175°C). Lightly grease a 24-cup mini muffin tin or line with mini paper liners.
Step 4: Form the cookie cups. Take small pieces of chilled dough (about 1 tablespoon each) and press them evenly into the bottom and up the sides of each mini muffin cup to form a base. Create a small well in the center for the filling.
Step 5: Prepare the pecan filling. In a separate bowl, whisk together the light corn syrup, light brown sugar, egg, 2 tablespoons melted butter, 1 teaspoon vanilla extract, and a pinch of salt until well combined. Stir in the chopped pecans.
Step 6: Fill and bake. Spoon the pecan filling evenly into each shortbread-lined muffin cup, filling them about two-thirds full. Bake for 12-15 minutes, or until the edges of the shortbread are lightly golden and the pecan filling is set and slightly puffed.
Step 7: Cool and serve. Let the cookies cool in the muffin tin for 5-10 minutes before carefully removing them to a wire rack to cool completely. The filling will firm up as it cools.