Mix flour, sugar, cocoa, baking soda and 1 teaspoon salt.
Make a well in the center and pour in the eggs, milk, water, oil and 1 teaspoon vanilla. Mix well.
Fill muffin cup of batter. Bake at 190 degrees C for 15 to 20 minutes, or until a toothpick inserted into the cake comes out clean.
Allow to cool.
For the filling, beat butter. Blend in icing sugar and pinch of salt.
Gradually beat in milk and vanilla. Beat until light and fluffy.
Fill a pastry bag with a small tip.
Push tip through bottom of paper liner to fill each cupcake.