Preheat the oven to 175°C (350°F). Line two baking sheets with parchment paper.
In a medium-sized mixing bowl, whisk together the flour, baking soda, baking powder, and salt. Ensure these ingredients are thoroughly combined.
1 1/4 cups All-purpose flour, ½ teaspoon Baking soda, ½ teaspoon Baking powder, ¾ teaspoon Salt
In a larger bowl, use an electric mixer or a whisk to beat the vegetable oil, dark brown sugar, and granulated sugar together until the mixture is well-blended. Add the egg, egg yolk, and vanilla extract, continuing to beat until the mixture is smooth and creamy.
1/3 cup Vegetable oil, 1/2 cup Dark brown sugar, 1/3 cup Granulated sugar, 2 teaspoons Pure vanilla extract, 1 Large egg, 1 Egg yolk
Mix the dry ingredients into the wet mixture. Stir until just combined to avoid overworking the dough, which can result in tough cookies.
Gently fold in the chocolate chips, distributing them evenly throughout the dough.
1½ cups Chocolate chips
Using a medium-sized cookie scoop or measuring 2 tablespoons per cookie, portion out the cookie dough onto the prepared baking sheets. Space the cookies sufficiently, allowing room for slight spreading during baking. Aim for no more than 8 cookies per sheet to ensure even baking.
Bake in the preheated oven for 9 to 11 minutes or until the cookies are golden around the edges but still soft in the center.
After removing the cookies from the oven, let them cool on the baking sheet for 5 minutes. While the cookies are still warm, sprinkle additional chocolate chips on top for a more decadent finish. This allows them to set and makes transferring easier.
Gently transfer the cookies to a wire rack to cool completely.