Step 1: Preheat your oven to 350°F (175°C).
Step 2: In a large mixing bowl, whisk together the all-purpose flour, baking soda, and salt.
Step 3: In another bowl, combine the melted butter, light brown sugar, and granulated sugar. Mix well until smooth, then add the egg, egg yolk, and vanilla extract, whisking until fully incorporated.
Step 4: Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Step 5: Gently fold in the chopped bittersweet and white chocolate until evenly distributed throughout the dough.
Step 6: Using a cookie scoop or tablespoon, drop rounded balls of dough onto a baking sheet lined with parchment paper, spacing them about 2 inches apart.
Step 7: Bake the cookies for 10-12 minutes, or until the edges are golden but the centers are still soft. Allow them to cool on the baking sheet for a few minutes before transferring them to a wire rack.
