In a small bowl, whisk together the egg, sour cream and vanilla bean paste until well combined. Set the mixture in the fridge.
In a medium-sized mixing bowl, add the flour, baking powder, salt, and sugar. Cube up the cold butter stick and add it to the dry ingredients.
Using a pastry cutter or your fingers, cut the butter into the flour mixture until the butter pieces are quite small.
Make a well in the center of the dry ingredients, then pour in the wet ingredients mixture. Lightly mix the ingredients together in the bowl until you have a shaggy dough.
Use your hands to lightly knead the scone dough together just until it becomes a cohesive ball.
Form the dough into a circle that is 6" in diameter and 1" thick. Cover the dough and let it rest in the freezer for at least 30 minutes.
Preheat the oven to 425°F / 220°C. Line a cookie sheet with parchment paper or a silicone baking mat.
Slice the scones into 8 equally sized triangles. Evenly space them apart on the lined baking sheet.
If desired, you can brush a little bit of heavy cream on top of the scones to encourage the tops to brown. Bake for 15-20 minutes, or until the scones start to turn golden brown on top and on the bottoms.
Vanilla Bean Glaze
Add the powdered sugar, vanilla bean paste, and 2 tbsp. of milk to a small mixing bowl. Whisk together, adding in more milk as needed to achieve your desired consistency.
Once the scones have cooled to room temperature, top them with the glaze. Serve and enjoy!