Preheat the oven to 400°F. Line a baking sheet with parchment paper or a silicone mat and set aside.
In a food processor, mix together the flour, sugar, baking powder, salt and butter until it resembles coarse meal.
Transfer the mixture to a large bowl. Add in the sour cream, and mix in until fully incorporated. I like using my hands to make sure it is all mixed in.
Lightly flour a large surface. Lightly flour a rolling pin and roll out the dough into an 8×10-inch rectangle. Arrange the raspberries in a single layer over the bottom two-thirds of the rectangle, and press them into the dough.
Fold the berryless third over the batter, then fold the bottom berry covered third over top. Pinch the ends to avoid berries falling out. Using a rolling pin, roll over top of the dough so that you end up with an even 1 inch block.
Cut the dough into 4 even pieces. Then, cut each piece diagonally into 2 triangles.
Place the scones on a plate, and transfer them to the freezer for around 5 minutes.
Remove the scones from the freezer and place on the prepared baking sheet. Brush a thin layer of the milk over the scones, then sprinkle the tops with the coarse sugar.
Bake in the preheated oven for 20 minutes. Remove from oven and allow them to cool on the pan for 5 minutes, then transfer to wire racks to cool completely.