Process pecans: Add 1/2 cup pecans to a food processor and pulse until finely ground. Set aside.
Make the dough: In a bowl, beat the butter and cream cheese together until smooth and creamy. Mix in the flour and ground pecans until a shaggy dough forms.
Chill the dough: Gather the dough into a solid ball, wrap it in plastic, and chill for 1 hour in the refrigerator.
Prep the muffin pan: Preheat your oven to 350°F. Spray a 24-cup mini muffin tin with cooking spray.
Form the crusts: Scoop out a tablespoon of dough for each muffin cup. Press it into the bottom and up the sides to create a crust. Freeze the pan while you prepare the filling.
Mix the filling: In a bowl, whisk together the egg, brown sugar, maple syrup, vanilla, salt, and bourbon (if using) until smooth and well combined.
Add pecans and filling: Remove the muffin pan from the freezer. Drop 1 teaspoon of chopped toasted pecans into the bottom of each crust. Pour in the filling nearly to the top.
Bake: Bake for 20 to 24 minutes, or until the filling puffs up slightly and the crust is golden brown. Let the tassies cool completely before gently removing them with an offset spatula.