Preheat oven to 400 degrees. Line a baking sheet with parchment paper or lightly grease.
Mix milk and sour cream together in a small bowl and place in the fridge. In a medium bowl, mix together flour, ½ cup sugar, baking powder, baking soda, and salt. Add the grated butter and mix in with a pastry cutter or two forks until the size of small peas. Drizzle the milk mixture in and fold in until combined.
Dust work surface lightly with flour and dump out dough and roll into a large rectangle 1/2 inch thick,about 10in x 15in. (Be sure to rotate and flip the dough while rolling, adding flour as needed so it doesn't stick.)
Sprinkle dough with the raspberries and white chocolate chips.
Roll dough up into a long log and then slightly press it down so that the top isn't so rounded. (Press extra raspberries and white chocolate into the top of the dough if desired.) Cut dough into four equal squares and then cut each square diagonally to make a total of 8 triangles. Place wedges of dough on prepared baking sheet, spacing them 2 inches apart. Brush the tops of dough with the melted butter.
Bake for 18-22 minutes until tops are lightly golden. Allow to cool for a few minutes and then add the glaze. Serve warm or at room temperature. Store uncovered at room temperature. Best if consumed within 2 days.