In a large bowl mix flour, baking soda, and salt until combined. In a saucepan over medium heat, brown butter and set aside to cool. In the bowl of a stand mixer with the paddle attachment, beat together butter and sugars until light and fluffy. Mix in egg, yolk, vanilla, and yogurt until incorporated. Gradually add the dry ingredients until combined. Fold in chocolate chips. Place cookie dough in the refrigerator for 2 hours to let the flavors meld together. Preheat the oven to 350 degrees F. Roll 1½ tablespoons of dough and flatten the dough to make a flat circle. Place 1 teaspoon of chilled Nutella in the middle then place another flat circle of cookie dough on top. Crimp edges to seal. Place dough balls on cookie sheet, 2 inches apart and bake 9-11 minutes or until the edges turn golden brown. Sprinkle with sea salt and let cool on wire racks.