In a separate bowl, whisk together the flour, cornstarch, baking soda, and salt. This ensures the leavening agent is evenly distributed throughout the dry ingredients.
Combine the soft butter, both sugars in a large bowl and beat using an electric hand mixer or a stand mixer for 2-3 minutes on medium speed until it is pale and fluffy.
Next, add the egg and vanilla extract, mixing just until the mixture is smooth and fully combined.
Gradually add the flour mixture to the wet ingredients, gently mixing with a spatula or whisk. When the dough is almost combined and a few streaks of flour still remain, fold in the chocolate chips and dried cranberries. Continue mixing just until everything is evenly distributed throughout the dough.
If you’re not baking right away, simply cover the dough (or the scooped portions) with plastic wrap and place them in the refrigerator to rest. Let the dough chill for at least 4 hours, or even overnight for the best flavor and texture.
When you’re ready to bake, start by preheating your oven to 350°F (175°C).
Use a medium cookie scoop to portion the dough, then roll each portion into a smooth ball. If you don't have a cookie scoop, simply weigh out about 35g of dough for each cookie. Arrange the dough balls on your prepared baking sheets, leaving about 2 inches of space between each one. For slightly flatter cookies, gently press down on the tops before baking. Finally, press a few extra chocolate chips and dried cranberries into each dough ball for a beautiful finish.
Bake the cookies for 9–10 minutes, or until the cookies are slightly puffed with soft centers and beautifully crackled tops.
Allow the cookies to cool on the baking sheets for 1–2 minutes before transferring them to a wire rack to cool completely.