Heat the oven to 175 C / 350 F. Line a 23 cm / 9-inch square baking pan with parchment paper, leaving overhang on two sides.

In a mixing bowl, whisk together the flour, granulated sugar, and salt for the crust. Pour in the melted butter and stir until the mixture looks like wet sand.

Press the crust mixture firmly and evenly into the bottom of the pan. Bake for 12 minutes, until the edges just turn golden. Set aside while you make the blondie layer.

In a separate bowl, whisk the melted butter and brown sugar together until smooth. Add the eggs one at a time, whisking well after each, then stir in the vanilla.

Add the flour, baking powder, and salt. Fold with a rubber spatula just until no dry streaks remain, don't overmix or the bars turn tough.

Fold in 150 g of the chopped white chocolate.

Pour the batter over the warm crust and spread to the edges. Scatter the raspberries evenly over the top, pressing a few in gently so they don't roll off.

Bake for 22 to 25 minutes, until the top is set and lightly golden, and a toothpick in the center comes out with a few moist crumbs, not wet batter.

Cool the bars in the pan for 30 minutes, then refrigerate for at least 90 minutes so the layers firm up enough to cut cleanly.

Melt the remaining 50 g white chocolate in 20-second bursts in the microwave, stirring between each, until smooth. Drizzle over the chilled bars.

Lift the bars out using the parchment overhang. Cut into 16 squares with a sharp knife, wiping the blade clean between cuts for neat edges.