Preheat oven to 180°C
Grease a large baking tray, or preferably use a silicone treated paper or a mat
Cream the butter and the sugar very well. The butter must become light and fluffy and the sugar dissolved.
Add the vanilla and salt.
Finally add the pecans and the flour and 50ml cocoa, mixing very thoroughly.
Using your hands shape spoonfuls of the dough into walnut sized pieces.
Arrange on the baking tray.
Bake for 30 minutes. They must be pale and crisp.
Place the icing sugar and half the cocoa in a large plastic bag or in a large mixing bowl. As the hot biscuits come out of the oven toss them into the plastic bag or mixing bowl and gently shake to coat the biscuits. At this stage the biscuits look quite messy as the sugar melts on the surface. Empty them onto the used baking tray and sift some additional cocoa (no extra sugar) over them. Leave the biscuits to cool completely.
Toss hot biscuits in the cocoa & icing sugar mixture
Finish with plain cocoa
Store in an airtight container.