Chocolate Chip Cookie Cake

Ingredients

• 1¾ cups (250 g/8.8 oz) all-purpose flour
• 1-2 teaspoon cornstarch (optional, but makes the cake super soft)
• 1 teaspoon baking soda
• ½ teaspoon salt
• ¾ cup (1 and ½ sticks/170 g) unsalted butter, softened to room temperature
• ½ cup (100 g/3.5 oz) granulated sugar
• ½ cup (100 g/3.5 oz) dark brown sugar
• 1 teaspoon vanilla extract
• 1 large egg plus 1 egg yolk
• 1 and ¼ cup (200 g/7.5 oz) semi-sweet chocolate chips