In a large bowl, whisk together melted butter, granulated sugar, brown sugar, eggs, milk, corn syrup, and vanilla until smooth.
1 cup melted unsalted butter, 1 ¼ cups granulated sugar, ¾ cup light brown sugar, 3 large eggs, 3 Tablespoons milk, 1 ½ Tablespoons corn syrup, 1 Tablespoon vanilla extract