Step 1

To the bowl of a stand mixer fitted with the paddle attachment (or large mixing bowl and electric mixer) combine the butter, Nutella, sugars, egg, vanilla, and beat on medium-high speed until creamed and well combined, about 4 minutes.

Step 2

Stop, scrape down the sides of the bowl, and add the flour, cornstarch, baking soda, optional salt, and beat on low speed until just combined, about 1 minute.

Step 3

Stop, scrape down the sides of the bowl, and add the white and chocolate chips, and beat on low speed until just combined, about 30 seconds.

Step 4

Using a large cookie scoop, 1/4 cup measure, or your hands, form approximately 11 equal-sized mounds of dough, roll into balls, and flatten slightly. Tip - Strategically place a few chocolate chips right on top of each mound of dough by taking chips from the underside and adding them on top.

Step 5

Place mounds on a large plate or tray, cover with plastic wrap, and refrigerate for at least 2 hours, up to 5 days. Do not bake with unchilled dough because cookies will bake thinner, flatter, and be more prone to spreading.

Step 6

Preheat oven to 350°C, line a baking sheet with a Silpat or spray with cooking spray. Place dough mounds on baking sheet, spaced at least 2 inches apart (I bake 8 cookies per sheet) and bake for about 9 minutes, or until edges have set and tops are just set, even if slightly undercooked and glossy in the center; don't overbake. Cookies firm up as they cool. Allow cookies to cool on baking sheet for about 10 minutes before serving. I let them cool on the baking sheet and don't use a rack.

Step 7

Cookies will keep airtight at room temperature for up to 1 week or in the freezer for up to 6 months. Alternatively, unbaked cookie dough can be stored in an airtight container in the refrigerator for up to 5 days, or in the freezer for up to 4 months, so consider baking only as many cookies as desired and save the remaining dough to be baked in the future when desired.