Ultra-chewy, bakery-style chocolate chip cookies made with melted butter, extra brown sugar, cornstarch, and an added egg yolk for thick, soft centers and rich caramel notes. The chilled, lumpy-tall dough bakes into wrinkly, chocolate-studded cookies that disappear fast.
Melt the butter and let it cool for 5 minutes.
In a bowl, whisk together the dry ingredients: flour, baking soda, cornstarch, and salt.
In a separate bowl, mix the melted butter with the brown sugar and granulated sugar until combined. Whisk in the egg, the extra egg yolk, and vanilla.
Combine the wet and dry ingredients to form a soft, slick dough. Fold in the chocolate chips (if they don’t stick at first because the dough is slick, keep stirring until it comes together).
Cover and chill the dough for at least 2–3 hours (or up to 3 days) for thicker cookies.
If the chilled dough is very firm, let it sit at room temperature for about 15 minutes. Line baking sheets with silicone baking mats or parchment.
Scoop dough into tall, textured balls: about 3 tablespoons for XL cookies or 2 heaping tablespoons (about 50g) for medium-large cookies. Shape into lumpy, taller-than-wide mounds for bakery-style thickness.
Bake until edges are set and centers still look soft. If cookies spread too much, use a spoon to gently reshape the edges while warm.
Cool on the baking sheet briefly, then transfer to a wire rack to finish cooling.