In a large bowl, toss together the flour, baking soda, cornstarch and salt. Set aside.
2 and ¼ cups (270g) all-purpose flour, 1 teaspoon baking soda, 2 teaspoons cornstarch, 1 teaspoon salt
In a medium sized bowl, whisk together the melted butter, brown sugar, and granulated sugar. When sugar clumps disappear, whisk in the egg, egg yolk, and vanilla.
1 cup (227g) unsalted butter, 1 cup (200g) firmly packed brown sugar, ½ cup (100g) granulated sugar, 1 large egg + 1 large egg yolk, 1 and ½ teaspoons vanilla extract
Pour wet ingredients into dry ingredients and mix together with a large spatula. Fold in the chocolate chips and stir until evenly dispersed.
1 and ½ cups (255g) chocolate chips2
Chill the dough: roll the chilled dough into balls (I use this #50 cookie scoop for all of my standard size cookies) and place balls of dough onto a large baking sheet, large platter, or something else flat that you can stick in the refrigerator so the dough can chill. You could also chill the whole bowl of dough, but this dough is difficult to scoop once chilled, and chilling is mandatory. Cover the dough balls/bowl of dough and chill in the refrigerator for at least 2 hours and up to 3 days.
When you are ready to bake the cookies, preheat the oven to 350ºF (177ºC). Line two large baking sheets with parchment paper or silicone baking mats and set aside.
Place 8 balls of dough per cookie sheet. If you like, you can press a few more chocolate chips on top/sides of the dough balls for aesthetic purposes.
Bake the cookies for 10-11 minutes or until edges just start to turn brown. Remove from oven and allow cookies to cool on the baking sheet for 5-10 minutes before moving to a wire rack to cool completely. Store cookies in an airtight container at room temperature, up to 7 days. Baked cookies may be frozen up to 3 months. You may also freeze rolled cookie dough up to 3 months. Bake frozen for 11-12 minutes.
Notes
Room temperature eggs: these are preferred for even distribution into batter. As a rule of thumb, when a recipe calls for room temperature or melted butter, it's generally a good idea to use room temperature eggs as well. If you don't have time to let eggs come to room temperature, place them in a bowl of warm water for 5-10 minutes before using.
Chocolate chips:I prefer 1 cup milk or semi-sweet chocolate chips and ½ cup mini semi-sweet chocolate chips.
Turn these into brown butter chocolate chip cookies: brown 1 cup of butter (here is my tutorial for how to brown butter), add 2 Tablespoons of water back into the brown butter once removed from heat, stir to mic well, then proceed with this recipe as written.
All nutritional values are approximate and provided to the reader as a courtesy. Changing ingredients and/or quantities will alter the estimated nutritional calculations.