1. Preheat oven to 350°F (175°C). Line a 12-cup muffin pan with cupcake liners.

For the Cupcakes

1. In a medium bowl, sift together the flour, baking soda, baking powder, and kosher salt. Set aside.
2. In a large bowl, beat the butter and sugar on high speed with an electric mixer until light and fluffy, about 2-3 minutes.
3. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract and sour cream until fully incorporated.
4. Turn the mixer to low speed and gradually add the sifted dry ingredients. Mix until just combined.
5. Gently fold the white chocolate chunks into the batter.
6. 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.

For the Raspberry Filling

1. 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. 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. Push the mixture through a fine-mesh sieve to remove seeds for a smoother filling.

For the Core and Fill

1. Use a cupcake corer, small knife, or spoon to cut out a small hole in the center of each cupcake.
2. Spoon the raspberry filling into the hole, filling it to the top. Replace the removed piece of cupcake over the filling.

For the White Chocolate Frosting

1. In a microwave-safe bowl, melt the white chocolate in 15-second intervals, stirring between each, until smooth. Let cool slightly.
2. 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. If using, mix in a few drops of pink food coloring for a vibrant finish.

For Frosting and Decoration

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