Preheat oven to 425°F. Prepare 18 count muffin pan by spraying with nonstick spray or line with cupcake liners.
In a large bowl using a handheld or stand mixer fitted with a paddle attachment, beat the butter, granulated sugar, and brown sugar on high speed until smooth and creamy, about 3 minutes. Scrape down the sides and bottom of the bowl as needed. Add the sour cream, eggs, vanilla, and milk. Beat on medium speed for 1 minute, then turn up to high speed until the mixture is combined. Scrape down the sides and bottom of the bowl as needed.
Add the flour, baking powder, baking soda, and salt and mix until just combined.
Stir in the raspberries and white chocolate chips. The batter will be thick.
Spoon the batter into the prepared muffin cups, filling them all the way to the top. Sprinkle the tops with coarse sugar.
Bake the muffins for 5 minutes at 425°F and then, keeping the muffins in the oven, reduce the oven temperature to 350°F and bake for an additional 18 minutes or until a toothpick inserted in the center comes out clean.
Allow muffins to cool completely and then enjoy!
Store muffins in airtight container.