Chocolate Chip Cookie Cake

Bahan-bahan (9 porsi)

• 3/4 cup (12 Tbsp; 170g) unsalted butter, softened to room temperature
• 1 cup (200g) packed light or dark brown sugar
• 1 large egg + 1 egg yolk, at room temperature
• 2 teaspoons pure vanilla extract
• 2 cups (250g) all-purpose flour (spooned & leveled)
• 2 teaspoons cornstarch (aka cornflour)*
• 1 teaspoon baking soda
• 1/2 teaspoon salt
• 1 and 1/2 cups (270g) semi-sweet chocolate chips
• optional: chocolate buttercream for topping