Mix 2 ¼ cup sifted all purpose flour, 1 ¼ tsp baking soda, and ¼ tsp salt in a mixing bowl and set aside.
Melt 1 cup butter in a saucepan over medium heat. Watch carefully and stir the butter to prevent it from scorching. Once the butter turns a toasty brown color, remove from heat immediately. Set aside to cool for a few minutes.
With an electric mixer, mix the brown butter, 1 ¼ cups brown sugar, and ¼ cup granulated sugar until blended.
Beat in 1 egg, 1 egg yolk, 1 ½ tsp vanilla, and 1 tbs yogurt until combined.
Slowly add dry ingredients and beat on low-speed just until combined.
Gently fold in ¾ cup semi-sweet chocolate chips, ½ cup milk chocolate chips, and ½ cup dark chocolate chips.
Chill dough for 2 or more hours.
Preheat oven at 350 degrees.
Roll 1 ½ tablespoons of dough into a ball. Flatten the dough ball very thinly into the palm of your hand. Place 1 teaspoon of chilled Nutella in the center. Fold dough around it, rolling into a ball -- it doesn’t have to be perfect. However, make sure Nutella is not seeping out of dough. Add more dough if necessary.
Place dough balls on cookie sheet, 2 inches apart and flatten tops with your hand VERY gently.
Bake the cookies 9-11 minutes or until the edges of the cookies begin to turn golden brown. They will look underdone in the middle, but will continue to cook once out of the oven. Cool cookies on the sheets at least 2 minutes. Sprinkle with a little sea salt. Remove the cooled cookies from the baking sheets after a few minutes and transfer to a wire rack to cool completely. Repeat with remaining dough.
Note: Chilling cookie dough solidifies the butter. As the cookies bake, the butter in the chilled cookie dough takes longer to melt. The longer the butter remains solid, the less cookies spread.