In a large bowl, whisk together the flour, sugar, baking powder, and salt.
Add the cold butter and work it into the flour using a pastry cutter, pastry blender, or your fingertips until the mixture resembles coarse crumbs. You should still see small pieces of butter throughout.
In a medium bowl, whisk together the sourdough discard, egg, heavy cream, and vanilla extract.
Add the wet ingredients to the flour mixture and gently stir with a wooden spoon or rubber spatula until a crumbly dough forms. Do not overmix.
Gently fold in the white chocolate and raspberries. If using frozen raspberries, keep them frozen until this step to avoid streaking the dough.
Turn the dough out onto a lightly floured surface and gently press it into a circle about 1 inch thick. Use a sharp knife or bench scraper to cut into 8 wedges.
Place the shaped, unbaked scones onto a parchment-lined baking sheet.
Fermentation Option (Overnight) Cover tightly with plastic wrap. Refrigerate for 8–24 hours.
Preheat the oven to 400°F.
Brush the tops with a little heavy cream or egg wash. Bake on a prepared baking sheet for 20-22 minutes, until the scones are set and lightly golden brown.
Let the scones cool slightly.
Drizzle with vanilla glaze or white chocolate.