Preheat oven to 400 degrees. Line a baking sheet with parchment.
In a large bowl, whisk together flour, baking powder, salt, sugar, cinnamon, and cardamom. Cut grated butter into the dry ingredients with a pastry cutter or fork until small crumbs form, no larger than a pea. Stir together buttermilk, vanilla, and 1 egg, then pour into the bowl and mix until just combined. Do not overmix. Gently fold in the peaches. The batter should be shaggy but decently cohesive.
Turn dough onto a clean, floured surface and gently knead 3-4 times. Form into a 1 inch thick rectangle. Cut 9 scones, or 12 small ones, out of the batter with a sharp knife. Set about 1 inch apart on the prepared baking sheet. Set the sheet in the freezer for 10 minutes.
Remove the scones from the freezer and lightly beat the remaining egg and brush over the scones. Bake 18-20 minutes until golden and poofy. Remove from oven and let cool 5 minutes on the baking sheet, then move to a wire rack to cool at least 10 additional minutes.
To make the glaze, whisk together powdered sugar, bourbon (if using), butter, vanilla extract, and cinnamon. If needed, add 1-2 tbsp milk to thin.
Drizzle glaze over the scones. The scones may be slightly warm but not hot for the glaze to not fully melt. Serve with coffee or tea!