Preheat the oven to 350°F (175°C). Line a 9-inch cast iron skillet or a 9-inch round baking pan with parchment paper and set aside.
In a large bowl, combine the softened light butter, applesauce, brown sugar, sweetener (or additional sugar), and vanilla extract; whisk until creamy.
Add the large egg to the bowl and whisk until fully incorporated.
Stir in the all-purpose flour, baking soda, and salt until just combined.
Fold in the powdered peanut butter (or melted creamy peanut butter if using) and half of the chocolate chips until evenly distributed, taking care not to overmix.
Spoon the batter into the prepared skillet or pan and spread evenly. Sprinkle the remaining chocolate chips over the top.
Bake for 20 minutes for a gooey center, or 25–30 minutes for a more set cookie. Remove from the oven and cool for about 10 minutes before slicing and serving.