Freeze the fats: Grate the butter and chop the shortening, then place them in the freezer for 30 minutes.

Prepare the peaches: Wash and dice the peaches, then pat them dry to remove excess moisture.

Mix the dry ingredients: Whisk together flour, baking powder, salt, and powdered sugar.

Combine fats and dry ingredients: Add grated butter and chopped shortening to the flour mix and blend until coarse crumbs.

Incorporate the peaches: Fold the prepared peaches into the flour-fat mix.

Add the buttermilk: Pour in the cold buttermilk and stir until a soft dough forms.

Shape the dough: Turn the dough onto a floured surface, knead gently, and shape into a rectangle.

Cut the biscuits: Use a biscuit cutter to cut out rounds and place on a baking sheet.

Chill and preheat: Refrigerate the biscuits for 20 minutes and preheat the oven to 450°F.

Apply the egg wash: Whisk the egg with milk and brush over the tops of the biscuits.

Bake the biscuits: Bake for 15-18 minutes until golden brown.

Prepare the glaze: Whisk together powdered sugar, melted butter, and milk, then drizzle over warm biscuits.