Line a baking sheet with parchment paper. Set aside.
In a large bowl, whisk together flour, sugar, cinnamon, allspice, baking powder and salt.
Use a box grater to shred butter into small pieces (it's best if the butter is frozen).1 Whisk butter into dry ingredients. In a separate bowl or measuring cup, whisk together 2/3 cup heavy cream and the egg. Pour the heavy cream mixture into flour mixture. Add the shredded apple at this time as well.
Use a wooden spoon or silicone spatula to mix ingredients together until large dough crumbles form (avoid over mixing!) Use your hands to form into a loose ball. If the dough is too dry and doesn't come together, add more heavy cream one tablespoon at a time. If it is too wet (like cookie dough), add another tablespoon or two of flour.
Transfer dough ball to a floured work surface and press into an 8-inch round disc. Use a bench scraper or sharp knife to cut into 8 triangles. Place scones on prepared baking sheet. Sprinkle with cinnamon sugar if desired.
Place baking sheet in the refrigerator to keep the scones cold while the oven preheats (about 15 minutes).
Preheat oven to 400° F. Once the oven beeps, wait 5 more minutes so ensure it is at 400 and hot!
Remove scones from the refrigerator and transfer them to the oven. Bake for 20 to 22 minutes or until the edges are golden brown. Let them cool on the pan for 5 minutes before transferring to a wire rack and adding glaze.
For the cinnamon glaze, whisk together confectioners’ sugar, cinnamon, milk and vanilla until smooth. Drizzle over scones. Serve warm or wait for glaze to harden and serve at room temperature.
Notes
Apples: Granny Smith, Honeycrisp or Braeburn are best for baking.Butter: Alternatively, cut butter into small 1/4-inch pieces. Add butter to flour mixture and cut butter into the mixture by using a pastry cutter or your hands.Store in an airtight container at room temperature for up to 3 days.Freeze scones (unbaked) in an airtight container or bag for up to 3 months. Baked scones last 1 month in the freezer.