Preheat the oven to 350°F and lightly grease a 9x13-inch baking dish with nonstick cooking spray.
In a large mixing bowl, whisk together the melted butter, granulated sugar, brown sugar, eggs, vanilla extract, and applesauce until smooth and fully combined.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring just until no streaks of flour remain. Fold in ¾ cup of the chocolate chips.
Pour the batter into the prepared baking dish and spread it evenly with a spatula. Sprinkle the remaining ¾ cup of chocolate chips evenly over the top.
Bake for 30 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Allow the cake to cool in the pan for 20 to 30 minutes before slicing and serving. For the cleanest cuts or if you plan to frost the cake, let it cool completely on a wire rack for 1½ to 2 hours. Enjoy as is or serve with whipped cream, vanilla ice cream, or your favorite frosting.
Enjoy it as is or top with whipped cream, ice cream, or your favorite frosting.