2 cups plus 2 Tbsp all-purpose flour
1/2 tsp baking soda
1/2 tsp salt
12 Tbsp (1 and 1/2 sticks) unsalted butter, melted and cooled
1 cup packed light brown sugar
1/2 cup granulated sugar
1 large egg
1 large egg yolk
2 tsp vanilla extract
1 and 1/2 cups semisweet chocolate chips
Adjust an oven rack to the lower-middle position and heat the oven to 325 degrees. Line 2 large baking sheets with parchment paper. Whisk the flour, baking soda, and salt together in a medium bowl.
In a large bowl, beat the melted butter and sugars together with an electric mixer on medium speed until smooth, 1 to 2 minutes. Beat in the egg, egg yolk, and vanilla until combined, about 30 seconds, scraping down the bowl and beaters as needed.
Reduce the mixer speed to low and slowly add the flour mixture until combined, about 30 seconds. Mix in the chips until incorporated.
Working with 2 tablespoons of dough at a time, roll the dough into balls and lay them on the prepared baking sheets, spaced about 2 inches apart. Bake the cookies, one sheet at a time, until the edges are set and beginning to brown but the centers are still soft and puffy, 15 to 20 minutes, rotating the baking sheet halfway through baking.
Let the cookies cool on the baking sheet for 10 minutes, then serve warm or transfer to a wire rack and let cool completely.