Place the shortening and butter in the freezer, at least 30 minutes prior to baking. Using a cheese grater, grate butter onto a plate or bowl and place back in the freezer while you continue.
Line a baking sheet with parchment paper and set aside.
Dice firm but ripe peaches into 1/4" pieces and place them in an even layer on a paper towel. Place another paper towel on top, pressing gently between paper towels to remove additional moisture and set aside.
1 ½ Cups Peaches
Whisk together flour, baking powder, salt, and powdered sugar in a large bowl. Add the frozen butter and shortening. Toss the butter and shortening into the flour until well coated.
2 Cups All-Purpose Flour, 1 Tablespoon Baking Powder, 1 ½ teaspoons Salt, ½ Cup Powdered Sugar
Add the diced peaches to the flour mixture and toss to coat.
Pour in the buttermilk. Gently stir using a rubber spatula until a soft dough forms.
1 Cup Buttermilk
Sprinkle flour onto your work surface and turn the dough out (the dough will be very sticky). Sprinkle more flour over the dough and your hands, then gently gather the dough into one pile, adding flour as needed to prevent sticking but keeping the dough slightly wet.
Pat the dough into a small 1-inch thick rectangle and gently fold it in thirds (like folding a letter), adding flour as needed to keep from sticking to the work surface.
Turn the dough and repeat 2-3 more times to create flaky layers then leave as a 1-inch thick rectangle.
Dip a 3-inch biscuit cutter in flour to cut down on sticking, then press straight into the dough and lift straight out without twisting.
Place the cut biscuits on the prepared baking sheet about an inch apart or touching depending on likes. Refrigerate for 20 minutes.
To Bake
While the dough is chilling, preheat the oven to 450℉.
Whisk together the egg and milk. Lightly brush the tops of the biscuits with the egg wash.
1 Egg, 2 Tablespoons Milk
Bake on the top rack for about 15-18 minutes, or until golden and hollow when you tap on them.
For the Glaze
Skip if you do not intend to glaze the biscuits and only brush with butter. While the biscuits are cooking, make the glaze by whisking together all the ingredients until smooth. Set aside.
1 Cup Powdered Sugar, 1 Tablespoon Butter, 2 Tablespoons Milk
When biscuits are done, remove the pan from the oven and brush with melted butter.
2 Tablespoons Butter
Allow the biscuits to cool for a couple of minutes, then drizzle glaze over the biscuits once, wait a few minutes then repeat with another layer of glaze.
Serve warm or at room temperature. Store leftovers in an airtight container in the fridge.
Video
Notes
Store leftovers in an airtight container in the fridge.