Preheat oven to 350 degrees F.
Combine flour, cocoa powder, salt and baking soda and set aside.
In a medium bowl, whisk together brown sugar, applesauce, sour cream, eggs and oil. Add dry ingredients to wet ingredients and mix just until combined. Melt 1/2 cup of chocolate chips in the microwave for about 1 minute. Stir into cake batter.
Transfer batter to a 9x13 pan sprayed with non-stick spray. Sprinkle remaining 1/2 cup chocolate chips on top of cake. Bake for 42-45 minutes, until toothpick inserted comes out clean. Cool completely. Cut into squares to serve.
Recipe can be halved & baked in an 8x8 square pan for 30-33 minutes.