Preheat the oven to 180°C (350°F) and line an 8×8 or 9×9 baking pan with parchment paper. In a large bowl, combine the cocoa powder, coconut flour, powdered sweetener, arrowroot starch, xanthan gum, baking soda, and salt. Mix thoroughly to ensure the dry ingredients are evenly distributed. Add the softened butter and vanilla extract, then mix until a thick, slightly crumbly dough forms.

Press about three-quarters of the crust mixture firmly into the bottom of the prepared baking pan, creating an even base layer. Set the remaining crust mixture aside — this will be used as the crumble topping. In a separate bowl, blend the softened cream cheese with the powdered sweetener, vanilla, and a pinch of salt until smooth and lump-free.

Beat the egg into the cheesecake filling mixture until fully incorporated and creamy. Pour the filling over the prepared crust, spreading it gently to cover the base completely. Sprinkle the reserved crust crumbs evenly over the top of the cheesecake layer, pressing them in lightly so they adhere. This creates a textured cookies-and-cream look.

Bake in the preheated oven for 25–30 minutes, or until the cheesecake layer is set and the edges are lightly golden. Allow the bars to cool on a wire rack, then chill in the refrigerator for at least 1 hour to firm up. Use a sharp knife (wiping it clean between cuts) to slice into individual bars before serving.