Triple chocolate cookies are an indulgent treat. The combination of semi-sweet, milk, and white chocolate makes for a cookie that is impossible to resist.
Add the flour, cocoa powder, cornstarch, baking powder, and baking soda to a medium-sized mixing bowl. Whisk to combine and set aside.
Using a stand mixer or a large mixing bowl and a handheld mixer on medium-high speed, beat the butter for 1 to 1½ minutes until smooth.
Add the sugars, heavy cream, and vanilla. Continue mixing for another 1½ to 2 minutes or until light and fluffy.
Reduce the speed to low. Add the eggs 1 at a time, mixing well after each egg.
Add the flour mixture. Mix just until combined and no flour streaks are visible.
Add in the semi-sweet chips, milk chocolate chips, and white chips. Mix just until incorporated. Cover and chill in the refrigerator for 1 hour.
Preheat the oven to 350°F. Line a baking sheet with parchment paper.
Use a 1½-tablespoon cookie scoop to scoop out the cookie dough. Space the dough balls about 2 inches apart.
Bake for 10 to 11 minutes (11 minutes was spot on for me, your oven may bake differently). Allow the cookies to rest on the cookie sheet for 5 to 7 minutes before transferring them to a cooling rack to cool completely.