White Chocolate Macadamia Nut Cookies Recipe

12 tablespoons (1.5 sticks) unsalted butter, softened at room temperature
¾ cup packed light brown sugar
¼ cup granulated sugar
1 large egg
2 cups all-purpose flour
2 teaspoons cornstarch
1 teaspoon baking soda
½ teaspoon salt
1 cup white chocolate chips
½ cup macadamia nuts, chopped