• Preheat the oven to 190°C (375°F), slightly cooler than a muffin bake so the tops stay flatter for icing. Line a 12-hole muffin tin with cupcake liners.
• Whisk together the flour, baking powder, baking soda and salt in a large bowl.
• In a separate bowl, whisk the sugar, sourdough discard, milk, eggs and vanilla until smooth.
• Drizzle in the oil, whisking until fully combined.
• Fold the wet ingredients into the dry, just until no dry flour remains.
• Toss the raspberries and white chocolate chips in the tablespoon of flour, then fold in gently and briefly, overmixing at this stage is what causes dense cupcakes and streaky purple batter.
• Divide between the liners, filling each about two-thirds full.
• Bake for 18-22 minutes, until a cocktail stick comes out clean or with a few moist crumbs (not wet batter).
• Cool in the tin for 5 minutes, then move to a wire rack and cool completely before icing.

Icing:

• Beat the cream cheese and butter together until smooth. Add the melted cooled white chocolate and vanilla and beat again until combined. Gradually beat in the icing sugar and salt until thick and pipeable. If it's too soft, chill for 15–20 minutes before piping. Pipe or spread onto fully cooled cupcakes and finish with a scatter of crushed freeze-dried raspberries.