• Preheat the oven to 175°C (350°F). Grease a 9×5" - 23x13cm (2 lbs) loaf pan and line with parchment paper, leaving a couple of inches of overhang on the sides for easy lifting later.
• In a bowl, whisk together the flour (minus the 1 tablespoon reserved for the raspberries and chocolate chips), baking powder and salt. Set aside.
• In another bowl or jug, whisk the Greek yogurt, sourdough discard and vanilla together until smooth and creamy.
• In a separate bowl, using an electric handheld mixer, beat the granulated sugar, light brown sugar and softened butter on medium speed for a few minutes, until light, fluffy and pale in colour.
• Beat in the eggs one at a time, mixing well after each addition until fully incorporated.
• Toss the raspberries in the reserved tablespoon of flour. This little step is what stops them sinking straight to the bottom of the cake.
• To avoid overmixing, fold the dry and wet mixtures into the batter in stages:
• ⅓ flour mixture → mix

  ½ yogurt/discard mixture → mix

  ½ remaining flour → mix

  remaining yogurt/discard mixture → mix

  remaining flour + chocolate chips (note 1) → mix
• Mix just until combined each time.
• Very gently fold in the floured raspberries with a rubber spatula, using as few strokes as possible. A little pink marbling is fine and looks intentional; a fully pink batter means you've gone too far.
• Transfer the batter to the prepared loaf pan and smooth the top into the corners.
• Bake for 1 hour 15-25 minutes, or until the top is golden, the edges are just pulling away from the sides of the pan, and a skewer inserted into the middle comes out clean with only a few moist crumbs. Check the loaf after an hour (note 2); if the top is browning too quickly, tent it loosely with foil.
• Cool in the pan on a wire rack for 15 minutes, then use the parchment overhang to lift the cake out and cool it completely on the rack before glazing.

Optional White Chocolate Glaze:

• For the glaze, melt 50g white chocolate and 1 tablespoon of unsalted butter together gently, either over a double boiler or in short bursts in the microwave, stirring between each. Stir in a pinch of salt. Let the glaze cool for a few minutes until it thickens slightly but is still pourable, then pour it over the top of the cooled cake, letting it drip down the sides. You may add some chocolate chips, candied citrus or freeze-dried raspberries whilst the glaze is still soft. Let it set before slicing (note 3).