Melt 1 tbsp unsalted butter in a small pan over medium heat. Add 1 large apple, diced, 3 tbsp light brown sugar, 1/2 tsp cinnamon and cook until the apple starts to soften and release juices, about 3 minutes. Once the mixture starts to look dry, add 1-2 tbsp water and cook until apples are softened, around 2-3 more minutes.
In a small bowl, combine 2 tsp cornstarch and 1 tbsp water until smooth. Pour into the pan and cook for another minute until bubbling. Set the apple filling aside to cool while you make the other fillings.
For the pecan pie filling
In a medium bowl, combine 1/3 cup brown sugar, 1/2 large egg, 1.5 tbsp unsalted butter, melted, 2 tsp all-purpose flour, Pinch kosher salt, 1/2 tsp apple cider vinegar or lemon juice and 1/2 tsp vanilla extract until smooth.
Fold in 1/4 cup chopped pecans and set aside.
For the pumpkin pie filling
In a medium bowl, stir together 1/3 cup pumpkin puree and 2.5 tbsp cream cheese, softened to room temperature until smooth. Add the rest of the ingredients (1/2 cup powdered sugar, 1/2 large egg, 1 tbsp unsalted butter, melted, 1/4 tsp cinnamon, 1/4 tsp nutmeg, 1/4 tsp vanilla and pinch kosher salt) and stir until smooth.
To assemble the pie
Roll out your chilled, prepared pie dough into a large circle about 1/4" thick. Use a 2-inch cookie cutter or glass to stamp out as many circles as possible, at least 24-26 rounds. Re-roll the dough scraps as needed (more rounds are nice to have in case a few get messed up, or if you're using a larger than 9-inch pie plate).
Place the dough rounds on a parchment-lined plate or baking tray and refrigerate for 5-10 minutes.
While the rounds are chilling, preheat the oven to 375 degrees and lightly grease a 9-inch pie pan.
Working with one dough round at a time, place a small spoonful of apple filling in the center of each round and pinch the edges to seal. Place a few of these pinched hand pies against one edge of the pie plate to start (apple is the easiest to work with because it's not as runny).
Working quickly, continue to fill the mini hand pies using alternating fillings. Because the pumpkin and pecan fillings are more runny, I recommend pinching empty rounds of dough and placing them between other pie rounds before filling them.
Bake at 375 for 45-55 minutes, or until the pie crust is lightly golden and flaky and the fillings look set. Let cool, then pull apart your mini hand pies and enjoy!