Preheat the oven to 350°F (180°C). Line the baking sheet with parchment paper or a silicone mat.
Combine the dry ingredients-flour, baking soda, and salt in a medium bowl.
In a stand mixer fitted with a paddle attachment, cream the butter, brown sugar, and granulated sugar on medium to high speed until light and fluffy. Scrape down the sides and bottom of the bowl.
Add half of the Nutella (40g) and vanilla, and beat again on medium to high speed until combined. Scrape down the sides and bottom of the bowl as needed.
Turn the mixer to low. Add the dry ingredients and milk and mix until thoroughly combined. Add the chocolate chips and mix until incorporated.
Add the remaining Nutella and mix on low speed for 5-10 seconds so the Nutella streaks through the dough and does not thoroughly combine.
Scoop 1½ tablespoon of dough, roll it into a ball, and place it on the baking sheet. If the dough is a little crumbly, roll the cookie ball with your hands. Repeat this with the remaining dough and place the cookie balls on the baking sheet, keeping enough space between them.
Stick more chocolate chips on the top of the cookie balls if preferred.
Bake the cookies for 9-11 minutes or until they are lightly firm around the edges. After removing them from the oven, the cookies will be extremely soft in the center, but they will be set eventually, so do not overbake.
Allow the cookies to cool on the baking sheet for at least 5 minutes. Then, transfer them to a wire rack to cool completely.