Preheat the oven to 350°F (175°C). Line a large baking sheet with parchment paper and set aside.
Add the melted butter, packed brown sugar, and granulated sugar to a large mixing bowl. Whisk until smooth and completely combined.
Add the whole egg, egg yolk, and vanilla extract. Mix until incorporated and the mixture looks smooth.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients. Mix just until no visible streaks of flour remain. Avoid overmixing the dough.
Gently fold in the white chocolate chips until evenly distributed.
Add the frozen raspberries last and fold them into the dough with as few strokes as possible. Work quickly so the berries remain frozen and don't release too much moisture.
Using a 1-ounce cookie scoop, portion rounded balls of dough onto the prepared baking sheet, leaving about 2 inches between each cookie.
Bake the White Chocolate Raspberry Cookies for approximately 12 minutes, or until the edges are lightly golden and the centers are puffed but still look slightly underdone.
Allow the cookies to cool on the baking sheet for several minutes so the soft centers can set. Transfer carefully to a wire rack and cool further before serving.