Caramelize the white chocolate: Line a half-sheet pan with parchment paper or a silicone baking mat. Set aside.

In a microwave-safe bowl, heat chopped white chocolate until melted, about 1 minute and 30 seconds (use 70% power if microwave is >1000W). Stir until smooth.

Place back in microwave at 15-20 second intervals, stirring between each until smooth. The chocolate will become thick and may seem to seize, but keep stirring. Continue heating and stirring until it reaches an amber color, lightly toasted smell, and smooth consistency (about 10 minutes total, depending on microwave power).

Using a spatula, spread the caramelized chocolate onto the prepared baking sheet as evenly as possible, to ¼-inch thickness. Place in the fridge to cool completely and solidify, about 20 minutes. Chop into bite-sized pieces, measuring out 150 grams. Reserve remaining chocolate for topping.

Make the cookies: Preheat oven to 350°F. Line baking sheets with parchment paper.

In a medium-sized bowl, whisk together the all-purpose flour, baking powder, baking soda, and fine sea salt. Set aside.