Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the softened unsalted butter, light brown sugar, and granulated sugar. Beat on medium speed until light and fluffy, about 2-3 minutes.
Add the large egg and vanilla extract to the butter mixture. Beat until well combined.
Add the heaping 1/3 cup of Nutella and stir gently to combine.
In a separate bowl, whisk together the all-purpose flour, cornstarch, baking soda, and optional pinch of salt.
Gradually add the dry ingredients to the wet ingredients. Mix on low speed until just combined.
Fold in the white chocolate chips and semi-sweet chocolate chips.
Using a cookie scoop or tablespoon, portion out the dough onto a lined baking sheet, leaving about 2 inches between each cookie.
Bake for 10-12 minutes, or until the edges are lightly golden.
Let the cookies cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.