Prepare the Pie Crust: In a large bowl, combine flour and salt. Cut in the cold, cubed butter until the mixture resembles coarse crumbs. Gradually add the ice water, buttermilk, or milk/vinegar mix, mixing until the dough just comes together. Add vinegar if using regular milk. Form the dough into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes.

Make the Pumpkin Filling: In a medium bowl, beat softened cream cheese until smooth. Add pumpkin puree, melted butter, and vanilla, mixing until well combined. Beat in the egg and egg yolk. Gradually mix in powdered sugar, cinnamon, pumpkin pie spice, and a pinch of salt until smooth and creamy.

Assemble and Bake: Preheat oven to 350°F (175°C). Roll out the chilled pie crust dough on a floured surface to about 1/8-inch thickness. Use a round cookie cutter to cut out circles. Press dough circles into mini muffin tins, ensuring they cover the bottom and sides. Spoon the pumpkin filling into each crust. Bake for 20-25 minutes, or until the filling is set and the crust is golden brown. Allow to cool completely.

Make the Whipped Cream: In a large mixing bowl, beat heavy cream until soft peaks form. Gradually add powdered sugar and vanilla (if using), and continue to beat until stiff peaks form. Dollop or pipe whipped cream onto cooled pumpkin pie bites just before serving.