2) Whisk together boiling water and cocoa. Cover and set aside.
3) With a mixer, cream together the butter, sugar, salt and vanilla essence. Add the eggs, 1 at a time, and continue creaming until light and fluffy.
4) Sift together the flour, bicarbonate of soda and baking powder and add this mixture, alternately with the buttermilk. Add cocoa and water mixture and mix until thoroughly combined. Scoop into cupcake pans and bake for 20 to 25 minutes.
5) Let cool completely before decorating. Dip tops of cooled cupcakes in the warm ganache and let set. Pipe more ganache on top for decoration. To fill, put buttercream in a pastry bag with a small round tip. Stick tip into the center of each cupcake and pipe in filling. Be careful not to pipe too much or you will break the cupcake. Serve.
6) For the ganache: Chop chocolate and place in a stainless steel or glass bowl. Bring cream and sugar just to a boil in a small saucepan and then pour over chocolate. Whisk together and then stir in butter until melted.
7) For the violet buttercream: Whisk together the egg whites and sugar in a stainless steel bowl. Place bowl in a water bath set over low heat. Whisk occasionally until sugar is dissolved and mixture is very warm, about 150 degrees F. Remove from water bath and whip with a hand-held mixer on high speed until stiff peaks. Lower speed and add the butter in small pieces. Add vanilla and violet essence and mix until smooth. Add violet color, 1 drop at a time, until desired shade is reached. Use to fill cupcakes as directed above.