Cut butter into small cubes and place into a bowl. Place bowl in freezer.
Combine water, sugar, salt and vinegar in a small bowl and place in freezer.
Measure flour into a medium bowl. Using a pastry cutter, cut butter into the flour until it combines into a coarse mixture.
Pour in a little bit of the water mixture at a time, until dough comes together. You may not need all of the water. The dough should be moist enough to shape into a disc, but not slimy.
Wrap dough in plastic wrap and chill for at least an hour.
Meanwhile, add peaches to a pot of boiling water and boil for about 30 seconds. Remove peaches from pot and place in a bowl of ice water to stop the cooking process.
Allow peaches to cool for 10 minutes or until you're able to handle them.
Peel the skin off the peaches by hand or start the peel with a knife if needed.
Slice peaches and remove pits, then cut peaches into inch chunks.
10 minutes before pie crust is finished chilling, add flour, sugars, and cornstarch to bowl with peaches. Toss to coat peaches. Allow to sit for 5 minutes then gently mix in raspberries.
Melt 2 tablespoons of butter and coat the inside and top of a muffin pan.
Pie Crust
Preheat oven to 350 degrees.
Use a rolling pin on a well-floured surface to roll out pie crust dough into a rectangle, about ⅛ inch thick.
Use a 4 in biscuit cutter to cut circles out of dough. You may want to test one size first to see if it's big enough for your muffin pan. The circle should cover the bottom and sides of a muffin slot. You'll need about 12-16 circles, depending on how far your dough goes.
Place half of the circles into the muffin pans, pressing sides of dough along the edge of the muffin spot. The dough should reach close to the top of the space.
Fill each muffin cup up about ⅔ of the way full of the peach raspberry mixture.
Place the second piece of dough on top of the peach mixture and use a fork to pinch the two pieces of dough together.
Use a sharp knife to cut small slits in the top of the crust to?vent the filling.
Sprinkle with a pinch of turbinado sugar, optional.
Bake mini pies for about 20 minutes, until crust is golden brown.
Notes
Use a container lid, mason jar lid, or coffee mug turned upside down if you don't have a biscuit cutter. Just be sure to test the size in your muffin pan first.