Preheat your oven to 350°F (175°C). This step is crucial for achieving that perfect bake.
In a large mixing bowl, add the cold butter cubes and packed light brown sugar. Using a mixer, cream them together until light and fluffy, about 2-3 minutes.
Add the eggs one at a time, mixing well after each addition. Then, mix in the smooth peanut butter and vanilla extract until fully combined.
In a separate bowl, whisk together the all-purpose flour, cornstarch, salt, baking soda, and baking powder.
Gradually add the dry ingredients to the wet mixture, mixing until just combined. Be careful not to overmix.
Gently fold in the white chocolate chips and chopped frozen white chocolate peanut butter candies.
Using a cookie scoop, portion out the dough onto a prepared baking sheet, leaving space between each cookie.
Bake the cookies in your preheated oven for 10-12 minutes, or until the edges are lightly golden but the centers remain soft.
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely. Enjoy!