Preheat oven to 350°F (175°C). Grease a standard 12-cup muffin tin generously with butter or baking spray.
Roll out pie crust to 1/8-inch thickness. Use a 3.5 to 4-inch round cutter to cut out 12 pastry discs.
Press each pastry circle into a muffin cup, pleating slightly around edges to fit snugly.
In a medium mixing bowl, whisk together eggs, brown sugar, pure maple syrup, melted butter, vanilla, flour, and salt until smooth and cohesive.
Divide chopped pecans evenly into the bottom of each pastry shell.
Ladle brown sugar custard filling over pecans, filling each cup about 3/4 full. Decorate tops with whole pecan halves.
Bake for 22 to 26 minutes until pastry edges are golden brown and centers are set. Cool in pan on wire rack for 20 minutes, then gently loosen with a butter knife and transfer to wire rack to cool completely.