Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.

In a large bowl, whisk together the flour, sugar, baking powder, and salt.

Cut in the cold butter using a pastry blender or your fingertips until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining.

In a small bowl, whisk together the beaten egg, 1/2 cup of heavy cream, and vanilla extract. Pour the wet mixture into the dry ingredients and mix gently until just combined. Fold in the diced peaches carefully, being careful not to overmix.

Turn the dough out onto a lightly floured surface. Gently pat or roll the dough into a 3/4-inch thick circle or rectangle. Cut the dough into 8 wedges or use a biscuit cutter.

Arrange the scones on the prepared baking sheet, spacing them about 1 inch apart. Brush the tops lightly with a little extra heavy cream.

Bake for 15 to 18 minutes, or until the tops are golden brown. Let cool on the baking sheet for 5 minutes before transferring to a wire rack.

If making the glaze, whisk together the powdered sugar, 2 tablespoons of heavy cream, and lemon zest until smooth. Drizzle generously over the cooled scones.