Line a baking sheet with parchment paper and set aside.

Dice peaches into tiny pieces and place them on a paper towel to absorb extra juice. Press gently between paper towels to remove additional moisture and set aside. (see note)

Whisk together flour, baking powder, salt, and powdered sugar in a large bowl.

Add shortening and grate butter into the dry ingredients. Use a pastry cutter to mix until the mixture looks like small crumbs.

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.

Sprinkle flour onto your work surface and turn the dough onto it (the dough will be very sticky). Sprinkle more flour over the dough and your hands, then gently gather the dough, 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). Turn the dough and repeat 2-3 more times; this will create flaky layers.

Finally, pat the biscuit dough into a 1-inch thick rectangle. Dip a 3-inch biscuit cutter in flour, then press straight into the dough without twisting. (Gather and press out the dough when needed)

Place the cut biscuits on the prepared baking sheet about an inch apart. (or sides touching for softer sides) Refrigerate for 20 minutes.

While the dough is chilling, preheat the oven to 450 F.

Lightly brush the tops of the biscuits with the egg wash.

Bake on the top rack for about 18 minutes (cook time may vary).

While the biscuits are cooking, make the glaze by stirring together all the ingredients until smooth. Set aside.

When biscuits are done, remove the pan from the oven and brush with melted butter.

Allow the biscuits to cool slightly, then brush your desired amount of glaze over the biscuits. (I let the glaze dry and do a few more layers of glaze) You can sprinkle on the reserved diced peaches now if desired.

Once the glaze has hardened, drizzle more glaze over the biscuits to lock in the diced peaches and allow the glaze to firm up.

Serve warm or at room temperature. Store leftovers in an airtight container in the fridge.