Prepare the raspberries: Set aside 12-15 perfect raspberries for garnish. Puree ¾ cup raspberries and strain for the frosting. Toss the remaining cup with 2 tablespoons flour.
Preheat oven to 350°F (177°C) and line a 12-cup muffin pan with cupcake liners.
Whisk together flour, baking powder, baking soda, and salt in a medium bowl.
Beat butter until smooth and creamy (about 1 minute), then add sugar and beat until light (about 2 minutes).
Add eggs one at a time, beating well after each addition. Beat in vanilla extract.
Add dry ingredients in three additions, alternating with sour cream and milk, beginning and ending with dry ingredients.
Fold in melted white chocolate until combined, then gently fold in flour-coated raspberries.
Fill cupcake liners ⅔ full and bake for 18-22 minutes until a toothpick comes out clean.
Cool in pan for 5 minutes, then transfer to wire rack to cool completely.
For frosting: Beat butter until creamy (about 2 minutes), then add powdered sugar, vanilla, and salt. Beat on low for 30 seconds, then medium-high for 2 minutes.
Add melted white chocolate and beat until creamy, then add heavy cream.
Fold in raspberry puree by hand until achieving swirls throughout the frosting.
Pipe frosting onto cooled cupcakes and garnish with fresh raspberry, white chocolate curls, and optional pearl sprinkles.