First, brown your butter: add butter to a large saucepan and place over medium heat. The butter will begin to crackle, and then eventually foam. Make sure you whisk constantly during this process. After a couple of minutes, the butter will begin to brown and turn a nice golden amber color on the bottom of the saucepan. Continue to whisk and remove from heat as soon as the butter begins to brown and give off a nutty aroma. Immediately transfer the butter to a medium bowl to prevent burning. Set aside to cool for 10 minutes or until cool enough to touch.
With an electric mixer, mix the brown butter and sugars until well combined, about 1 minute. Beat in the egg, egg yolk, vanilla, and yogurt until combined.
In a separate large bowl, whisk together the flour, baking soda, and salt. Slowly add the dry ingredients to the wet ingredients and beat on low-speed just until combined. Add both chocolate chips and mix on low speed until just incorporated into the dough.
Chill your dough for 2 hours in the refrigerator, or up to 12-24 hours. Do not try to speed up this process. The dough needs to chill in order to be perfect.
Helpful tip: If you want to make it easier to bake the cookies, I suggest rolling them into balls BEFORE chilling the dough. That way you can simply place them on the prepared baking sheet and bake! Up to you. I usually put my dough in the fridge for 10 minutes, then I take it out roll them into balls, place on a plate or baking sheet and place in the fridge for another hour or two.
Once dough is chilled, preheat the oven to 350 degrees F and line a baking sheet with parchment paper. You might need to take out the dough and thaw it out a bit before measuring the dough if it is super hard and you did not already roll the cookie dough into balls. This should take about 20 minutes. Once ready to bake, measure 2 heaping tablespoons of the dough or use a medium cookie scoop. It doesn't have to be perfectly rolled. Place dough balls on cookie sheet, 2 inches apart.
Bake the cookies 9-11 minutes or until the edges of the cookies begin to turn golden brown. They will look a bit underdone in the middle, but will continue to cook once out of the oven.
Cool the cookies on the sheets for 5 minutes to allow them to set up, then sprinkle each cookie with sea salt. Remove the cooled cookies from the baking sheets and transfer to a wire rack to cool completely. Makes 24-36 cookies.