Heat the oven to 350°F/175°C. Line a standard loaf pan (8.5 x 4.5-inch/21 x 11 cm) with parchment paper, leaving an overhang on two sides.

In a small saucepan, melt the butter over low heat, or melt in a microwave-safe bowl using short pulses. Set aside to cool slightly.

In a large mixing bowl, whisk the melted butter with the brown sugar, white sugar, egg, yolk, and vanilla until smooth and glossy. Add the flour and baking soda and stir until just combined. Fold in three-quarters of the white chocolate, reserving the rest for topping.

Spoon the Lotus spread in small dollops across the bottom of the prepared pan. Pour in the batter and gently smooth the top with a spatula. Press the broken cookies into the surface and scatter over the remaining white chocolate.

Transfer the pan to the freezer and chill for 30 minutes. This helps create a fudgier center and neater edges.

Bake until the top is golden and the center is just set, 22 to 25 minutes. If using a hot or convection oven, check at 20 minutes. For a cakier texture, bake for up to 28 minutes, though the blondies will be less gooey.

Let the blondies cool slightly, then return to the freezer for 30 minutes to firm before slicing. Sprinkle with flaky salt just before serving. Store leftovers in an airtight container in the refrigerator for up to 4 days.