Make Chewy Chocolate Chip Cookies: bake soft, gooey cookies with golden edges and melty chips.
In a large bowl whisk the flour, baking soda, cornstarch and salt until evenly combined and aerated. Take a moment to break up any small lumps so the dry mixture is uniform and powdery — this is the foundation for a tender, chewy cookie. Use a wide bowl so there’s room when you add the wet ingredients; set this bowl nearby, uncovered.
In a medium bowl whisk the melted, slightly cooled butter together with the packed brown sugar and granulated sugar until the mixture is smooth and there are no stubborn clumps. Whisk in the whole egg and the extra egg yolk until fully incorporated, then stir in the vanilla. The wet mixture will be noticeably thin and glossy from the melted butter — that shine is what helps the cookies spread and stay chewy once baked.
Pour the wet mixture into the dry ingredients and mix gently with a large spoon or spatula until just combined. The dough will feel very soft, thick and shiny; don’t overwork it — stop when there are no visible streaks of flour. Fold in the chocolate chips with broad, gentle strokes; they may not cling immediately because of the melted butter, but do your best to distribute them throughout the glossy dough.
Cover the bowl tightly and refrigerate for at least two hours and up to three days — overnight is ideal. Chilling firms the dough so the cookies bake up taller with chewy centers instead of spreading flat. If the dough chills longer than two hours, let it rest at room temperature for about 15 minutes before scooping so it’s scoopable but still cold.

Using a cookie scoop or tablespoon, portion the chilled dough into balls around 50–60g each for medium-large to XL cookies. Roll each scoop into a ball and then gently shape it tall rather than wide — press and cup with your fingers to create a slightly cylindrical mound. Arrange the dough balls about 3 inches apart on baking sheets lined with parchment or silicone mats.
Bake at the specified moderate temperature until the edges are just very lightly browned and the centers still look soft — they will finish setting as they cool. Cool the cookies on the baking sheet for about 10 minutes, then transfer them to a wire rack to cool completely. While still warm you can press a few extra chocolate chips on top for an extra glossy look.
Once fully cooled, keep the cookies tightly covered at room temperature for up to one week. Serve on a wire cooling rack or stacked on a simple plate; the cookies should present with golden-brown crinkled edges, soft slightly gooey centers and pockets of melted semi‑sweet chocolate.
