Step 1

Cream the butter and sugars together with a hand or stand mixer fitted with a paddle attachment on medium speed until light and fluffy. Scrape down the sides and bottom as needed. Beat in the egg and vanilla on high speed until combined, scraping down the sides as needed. In a separate bowl, combine the flour, cocoa powder, baking soda, and salt. Slowly mix it into the wet ingredients on low speed. The dough will be thick. Again on low speed, mix in the milk until combined. The dough will be sticky. Fold in 1 cup of white chocolate chips.

Step 2

Cream the butter and sugars together with a hand or stand mixer fitted with a paddle attachment on medium speed until light and fluffy. Scrape down the sides and bottom as needed. Beat in the egg and vanilla on high speed until combined, scraping down the sides as needed. In a separate bowl, combine the flour, cornstarch, baking soda, and salt. Slowly mix it into the wet ingredients on low speed. The dough will be thick. Fold in 1 cup of chocolate chips.

Step 3

Cover both cookie doughs with aluminum foil and chill for at least 3-4 hours or up to 3 days. Chilling is imperative; the cookies will spread into flat puddles if the cookie doughs are not chilled.

Step 4

Preheat oven to 350°F (177°C). Line cookie sheet with silicone baking mat or parchment paper. Measure 1.5 Tablespoons of chocolate cookie dough. Roll into a ball. Take 1.5 Tablespoons of chocolate chip cookie dough. Roll into a ball. Press the two balls together between your hands and roll them into 1 large ball. Repeat rolling for each cookie. The chocolate cookie dough is particularly sticky and will stick to your hands, so wash/wipe them after you roll each cookie. It’s important the chocolate cookie dough is chilled or else it will be even more messy.

Step 5

Bake the cookies for 11-12 minutes. The cookies will look very soft, puffy, and almost undone. Remove from the oven. With the remaining white chocolate and semi-sweet chocolate chips you have leftover, press a few into each cookie. (This is just for looks and not required.) Cool cookies for 10 minutes on the baking sheets before transferring to a wire rack to cool completely.

Step 6

Cover leftover cookies tightly and store at room temperature for up to 1 week.