Preheat the oven to 350°F (175°C) and grease a baking pan or line it with parchment paper.
In a large mixing bowl, combine the unsweetened cocoa powder, erythritol or monk fruit sweetener, and salt.
Melt the coconut oil or cocoa butter in a microwave or double boiler until fully liquid, then add it to the dry ingredients along with the vanilla extract.
Mix in the unsweetened applesauce until well combined.
In a separate bowl, whisk together the almond flour and baking powder. Gradually incorporate the dry ingredients into the wet mixture until a smooth batter forms.
Fold in the sugar-free chocolate chips, ensuring they are evenly distributed throughout the batter.
Pour the batter into the prepared baking pan and spread it evenly.
Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
While the cake is baking, you can prepare a simple chocolate mousse: combine ¼ cup unsweetened cocoa powder, 3 tbsp sugar-free maple syrup, 1 tsp vanilla extract, and 2 tbsp almond milk in a bowl. Mix until smooth and creamy.
Allow the cake to cool for 10 minutes in the pan before transferring it to a wire rack to cool completely. Serve slices with a dollop of the chocolate mousse.