Preheat oven to 350℉. Line 2 cookie sheets with parchment paper. Set one aside.
Using a tablespoon or small cookie scoop, place dollops of Nutella on the cookie sheet. Transfer to the freezer to chill while you prepare the cookie dough.
Melt butter in a medium saucepan over medium heat. When butter is completely melted, add chocolate chips and stir constantly until the chocolate melts.
Remove saucepan from heat. Stir in milk, vanilla, instant coffee, and unsweetened cocoa powder.
In a large mixing bowl, use an electric mixer on medium speed to beat together sugar and eggs, about 1-2 minutes. Stir in the melted chocolate mixture and continue mixing for another 2 minutes, until well combined.
In a medium-sized bowl, whisk together flour, baking soda, and salt. Add half of the flour mixture to the chocolate mixture, and mix on low speed to combine. Add the remaining flour mixture and mix on low speed, until just barely combined.
Remove Nutella dollops from the freezer. Place scoops of cookie dough on prepared cookie sheet, and use a spoon to create a well in the middle of the dough. Place one Nutella dollop into each well.Fold the cookie dough over the Nutella, then roll dough in the palm of your hands to form a ball, ensuring that the Nutella is fully covered by the dough.
Arrange unbaked cookies on the baking sheet in a single layer, about 2 inches apart. Allow plenty of room for them to spread as they bake.
Bake in preheated oven for 8-10 minutes. Allow cookies to cool for 5 minutes before moving them to a wire rack to cool completely.
Notes
Storage - Nutella cookies will last about 5 days in an airtight container at room temperature. However, you can also store freeze them for up to 4 months. Thaw them in a microwave on high power for about 30 seconds for a decadent treat.
Make them smaller - If you would like small to medium-sized cookies, use a half tablespoon to scoop dollops of Nutella and use the same amount of dough you would use for a regular cookie.