1. Preheat oven to 425°F (220°C) and line a baking sheet with parchment.
2. In a large bowl, whisk together the flour, baking powder, baking soda, salt, and granulated sugar.
3. Add the cold butter and work it in using a pastry cutter or fingers until the mixture resembles coarse crumbs.
4. Stir in grated carrot, pecans, cinnamon, nutmeg, allspice, and dark brown sugar until evenly dispersed.
5. In a small bowl, whisk together the egg, heavy cream, and vanilla extract.
6. Add the wet mixture to the dry and gently mix with a spatula until a shaggy dough forms.
7. Turn out the dough onto a well-floured surface and press together by hand until cohesive. Do not overwork.
8. Pat the dough into a round about 1 inch thick. Wrap in plastic wrap and chill in the freezer for 45 minutes.
9. Turn the dough onto a floured surface, cut into rounds or wedges, and place on prepared sheet.
10. Freeze for another 30 minutes, then brush tops with heavy cream.
11. Bake for 18-22 minutes, or until golden brown and the interior reaches 200°F.
12. Let scones cool 10-15 minutes before glazing.
13. For the glaze, beat the cream cheese and butter until smooth.
14. Add powdered sugar, salt, and vanilla, and mix until no lumps remain.
15. Add heavy cream, 1 tsp at a time, until the glaze is drizzle-able.
16. Drizzle glaze generously over cooled scones.
