Line a cookie sheet with parchment paper. Scoop out ½ Tbsp Nutella and place onto the pan. Continue until you have at least 18 balls. (You may want to scoop a couple extra balls just in case). Place balls in freezer until ready to use.
Sift flour, baking soda, and salt together in a medium bowl. Set aside.
In a mixing bowl, cream together the butter, brown sugar, and sugar until well blended. Add vanilla, egg, and egg yolk and mix until smooth.
Add dry ingredients just until blended. Stir in the chocolate chips. Refrigerate batter for at least 1 hour.
Preheat oven to 325 degrees. Line baking sheets with parchment paper.
Remove Nutella balls from freezer.
Scoop 1 Tbsp cookie dough out of bowl and flatten slightly. Place a Nutella ball in the middle and scoop another 1 Tbsp cookie dough out and place on top of Nutella ball. Form sides of cookie dough around Nutella to cover it completely and roll into a ball. Place each ball on the cookie sheet (note: these cookies will be bigger than your average cookie!)
Bake for 15-18 minutes until edges are golden. Cool on sheets for 2 minutes; transfer to cooling rack. Enjoy!
Recipe by Simple, Sweet & Savory at https://www.simplesweetsavory.com/nutella-stuffed-chocolate-chip-cookies/