Preheat the oven to 400°F (200°C) and line a baking tray with parchment paper.

Mix flour, sugar, baking powder, salt, and baking soda in a medium bowl. Grate frozen butter into the mixture and work in with fingers until coarse crumbs form, then add raisins.

Whisk sour cream and egg in a small bowl until combined.

Stir sour cream mixture into the flour mixture using a fork. Work the mixture into a dough ball by hand.

Place dough on a lightly floured surface and pat into a 7-8 inch circle, about ¾-inch thick. Sprinkle with sugar.

Cut into 8 triangles with a sharp knife and place on baking tray 1 inch apart.

Bake scones in the oven for 15-17 minutes until golden. Cool for 5 minutes.