Preheat your oven to 350°F (175°C) and line a muffin pan with cupcake liners.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and fine salt until well combined.

In a separate bowl, whisk together the full-fat sour cream, water, vegetable oil, egg, and vanilla extract until you achieve a smooth mixture.

Pour the wet mixture into the bowl of dry ingredients, stirring gently until just combined.

Carefully divide the batter among the cupcake liners, filling each about three-quarters full.

Place the muffin pan in the preheated oven and bake for 18-20 minutes.

Once baked, remove the cupcakes from the oven and allow them to cool in the pan for 10 minutes.

For the frosting, melt the white chocolate and allow it to cool slightly. Cream together the unsalted butter, powdered sugar, vanilla extract, and a pinch of salt until fluffy.

Add the melted white chocolate and heavy cream, mixing until smooth.

Using a piping bag filled with raspberry jam, carefully inject the jam into each cupcake center.

Pipe the white chocolate buttercream frosting onto each cupcake.

To make the ganache, melt more white chocolate with heavy cream until smooth, then drizzle over the frosted cupcakes.

Garnish each cupcake with fresh raspberries and chocolate shavings before serving.