Preheat the oven to 350°F and line a 12-cup muffin tin with paper cupcake liners.
In a medium bowl, whisk together the flour, baking powder, and salt until well combined.
In a large bowl, beat 1/2 cup softened butter and granulated sugar with a mixer on medium speed until light and fluffy, about 2 to 3 minutes.
Add the eggs one at a time, beating well after each addition, then mix in the vanilla bean paste.
With the mixer on low speed, add the dry ingredients in three additions, alternating with the milk, beginning and ending with the dry ingredients, mixing just until the batter is smooth.
Divide the batter evenly among the 12 liners, filling each about 2/3 full.
Bake for 18 to 20 minutes, until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Let the cupcakes cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.
While the cupcakes cool, place the raspberry jam in a piping bag or small zip-top bag and set aside.
Melt the white chocolate in a heatproof bowl set over a pan of barely simmering water, stirring until smooth, then remove from heat and let cool to room temperature.
In a large bowl, beat 1/2 cup softened butter for the frosting until creamy, about 1 minute.
Gradually add the powdered sugar, mixing on low speed until incorporated, then increase to medium and beat until fluffy.
Add the cooled melted white chocolate, heavy cream, vanilla bean paste, and salt, and beat until the frosting is smooth and light.
Once the cupcakes are completely cool, use a small knife or cupcake corer to cut a small cylinder out of the center of each cupcake, going about two-thirds of the way down.
Pipe or spoon raspberry jam into the center of each cupcake cavity until filled, then gently press a small piece of the removed cake back on top if desired.
Transfer the white chocolate buttercream to a piping bag fitted with a star tip or round tip and pipe swirls of frosting onto each filled cupcake.
Garnish the tops with fresh raspberries or white chocolate shavings.
Store the cupcakes in an airtight container at room temperature for up to 2 days or refrigerate for up to 1 week. Bring to room temperature before serving.