Make the Cupcakes:

1. Preheat and Prepare:
   • Preheat your oven to 350°F (175°C).
   • Line a 12-cup muffin pan with cupcake liners.
2. Sift Dry Ingredients:
   • In a medium bowl, sift together the flour, baking soda, baking powder, and kosher salt. Set aside.
3. Cream Butter and Sugar:
   • In a large bowl, beat the butter and sugar on high speed with an electric mixer until light and fluffy, about 2-3 minutes.
4. Incorporate Wet Ingredients:
   • Add the eggs one at a time, beating well after each addition.
   • Mix in the vanilla extract and sour cream until fully incorporated.
5. Combine Wet and Dry:
   • Turn the mixer to low speed and gradually add the sifted dry ingredients. Mix until just combined.
6. Fold in White Chocolate:
   • Gently fold the white chocolate chunks into the batter.
7. Fill and Bake:
   • Divide the batter evenly among the cupcake liners, filling each about 3/4 full.
   • Bake for 15-18 minutes, or until a toothpick inserted into the center comes out clean.
   • Let the cupcakes cool completely on a wire rack.

Prepare the Raspberry Filling:

1. Cook the Raspberries:
   • In a small saucepan, combine raspberries, water, and sugar. Cook over medium heat until the raspberries break down and the mixture begins to simmer.
2. Thicken the Filling:
   • Stir the cornstarch slurry (cornstarch mixed with water) into the raspberry mixture.
   • Cook for another 1-2 minutes, or until the mixture thickens. Remove from heat and let cool.
3. Remove Seeds (Optional):
   • Push the mixture through a fine-mesh sieve to remove seeds for a smoother filling.

Core and Fill the Cupcakes:

1. Core the Cupcakes:
   • Use a cupcake corer, small knife, or spoon to cut out a small hole in the center of each cupcake.
2. Fill with Raspberry Sauce:
   • Spoon the raspberry filling into the hole, filling it to the top.
   • Replace the removed piece of cupcake over the filling.

Make the White Chocolate Frosting:

1. Melt the Chocolate:
   • In a microwave-safe bowl, melt the white chocolate in 15-second intervals, stirring between each, until smooth. Let cool slightly.
2. Whip the Frosting:
   • In a large bowl, beat the butter until smooth. Gradually add the confectioners’ sugar, melted white chocolate, and vanilla extract.
   • Add milk one tablespoon at a time until the frosting reaches your desired consistency.
3. Color the Frosting (Optional):
   • If using, mix in a few drops of pink food coloring for a vibrant finish.

Frost and Decorate:

1. Pipe or Spread Frosting:
   • Use a piping bag with a star tip or a spoon to swirl the frosting onto the cooled cupcakes.
2. Decorate:
   • Garnish with extra white chocolate shavings, fresh raspberries, or sprinkles if desired.