Firstly - there is no secret. Authentic African black soap is made in different African countries according to local recipes. Whatever the ingredients are, they should be pure, if possible organic and the soap itself should be hand made in small batches preferably by small local women's co-operatives. Some black soaps contain essential oils or lemon juice (popular in Ghana) others are unscented.
Personally I prefer the black soap from Togo as it contains high levels of unrefined shea butter and unrefined palm kernel oil. Both are fair trade and sustainably harvested meaning no rainforests were chopped down (unlike palm oil that comes from Malaysia for example).
You can melt down the individual bar together with unrefined shea butter and add your preferred essential oil. Or just add distilled water plus your favourite essential oil to your soap flakes to make liquid black soap that can be stored in a pump dispenser. If you don't want to do this then just buy a bottle of ready-made liquid black soap and add your essential oils to this.
African black soap is extremely versatile. It can be used to wash your hands of course. It's great as a shampoo or add some liquid soap to your hot bath. For me the benefits are multi fold: it helps my skin stay spot free, doesn't dry my skin out, the bar is ideal when travelling (none of this plastic bag business at the airport that is now in place for liquids) and it is really multi functional as it is an all round beauty product.
I like the fact that our African black soap is made with organic principles in mind: no chemicals, parabens, steroids, animal by products are added and of course it is not tested on animals either. It is suitable for vegans and I have countless emails from people telling me about how the soap helped better their skin's condition.
More fantastic shea butter soaps, creams and lotions as well as shampoo and conditioner made with shea butter can be found here.