First Step: Preheat and prepare baking pan
Set your oven to 350°F (175°C). Grease an 11.5-inch round cake pan or line it with parchment paper to prevent sticking and ease removal.

Second Step: Mix melted butter and sugars
In a large bowl, combine the melted unsalted butter, packed light brown sugar, and granulated sugar. Stir by hand until well blended and smooth. This step is key to creating a dense, chewy cookie cake.

Third Step: Incorporate egg and vanilla
Add the large egg and vanilla extract into the sugar-butter mixture. Beat thoroughly until the mixture is glossy and uniform, ensuring good moisture distribution throughout the dough.

Fourth Step: Add dry ingredients
In a separate bowl, whisk together the all-purpose flour, baking soda, baking powder, and salt. Gradually fold the dry ingredients into the wet mixture, mixing gently until you form a dense dough without overworking.

Fifth Step: Fold in chocolate chips
Separate the chocolate chips: chop half and keep the others whole. Gently fold both into the dough, ensuring even distribution to avoid clumps which can cause uneven baking or breaking.

Sixth Step: Press dough into pan
Transfer the cookie dough into your prepared pan. Using your hands or a spatula, press it evenly to about ½-inch thickness, creating a uniform layer for thorough baking.

Seventh Step: Bake the cookie cake
Bake for 12-14 minutes until the top has a slight golden color and the center is just set but still soft to the touch. Avoid overbaking to keep the cookie cake chewy and tender.

Final Step: Cool and optionally frost
Allow the cookie cake to cool completely in the pan before carefully loosening and transferring to a wire rack. For added indulgence, prepare a vanilla buttercream frosting by beating softened butter with powdered sugar, vanilla, salt, and milk until creamy. Frost edges and decorate with sprinkles, if desired.