Shred the unsalted butter using a cheese grater. Do this directly onto a plate or a bowl. Cover with plastic wrap, and transfer to the freezer to keep cold.

Combine the milk with the apple cider vinegar in a liquid measuring cup. Refrigerate until ready to use. (The milk will curdle a little. That's OK! We want that to give us a buttermilk-esque flavor.)

In a large bowl, whisk together the flour with the sugar, cornstarch and salt until incorporated.

Remove the butter from the freezer and add it to the flour mixture. Stir gently with a rubber spatula (or your hands) until the ingredients are combined. The butter appears to be the size of peas and the texture of wet sand.

Drizzle half of the milk mixture over the dry ingredients. Use a plastic spatula to lightly mix the flour with the liquid. Repeat the process by drizzling more in, repeating until the dough holds together. You can test this by picking up some with your hand and squeezing or you can press the dough against the side of the bowl. (You should still be able to see chunks of butter in it.) If necessary, add extra cold milk, 1 tablespoon at a time, until the dough holds together.

Form the dough into a disk and wrap it tightly in plastic wrap.

Refrigerate for at least 1 hour.

If desired, peel the peaches before slicing them. (A peach peel does not bother me, but I know the texture can throw some off. Consider blanching the peaches before peeling to make the process easier.)

Measure out the sliced peaches and blackberries in a medium-sized bowl.

Add the sugar and cornstarch. Toss until combined, then set aside.

Preheat the oven to 350°F. Line a large baking sheet with parchment paper or a nonstick baking mat. Set aside.

Lightly flour a clean, flat surface, and roll out the pie crust. Using a 4½" to 5" round cookie cutter (or a plate of a similar size), cut rounds into the dough for the individual pies.

Transfer the dough rounds to the prepared baking sheet, then measure out about 2 tablespoons of the filling into them.

Brush egg around the edges of half the round, then seal with your fingers or a fork.

Repeat the process until all 10 pies have been made.

Brush the tops of the hand pies with the egg.

Gently cut two vents in the top of each.

Sprinkle with additional sugar, if desired.

Transfer the baking sheet to the oven, and bake for 30-40 minutes, or until the tops are golden brown.

When cooled, remove from the oven, and let cool for 5 minutes before devouring!

In a bowl, combine the whipping cream with the bourbon.

Using a hand mixer, whip the cream and bourbon together until they start solidifying.

Sprinkle in the powdered sugar, and continue whipping until the desired whipped cream consistency.

Serve with the warm hand pies!