Lisa's Mexican Chocolate Biscuits

This is a recipe from Lisa Hurry, the biscuits are fantastic!  I use hot chilli powder rather than cayenne pepper but we like them with plenty of kick.

1 1\2 cups plain flour
3/4 cups good dark cocoa powder (I use Alalanche for these)
1/4 tsp salt
1/4 tsp finely ground black pepper
1/4 tsp cayenne pepper (more or less as you like, but don't be frightened)
3/4 tsp cinnamon
185g soft butter
1 1/2 tsp vanilla
1 cup soft brown sugar
1 egg

Oven to 180. line two trays with baking paper.
Sift together flour, cocoa, salt, pepper, cayenne and cinnamon.
Cream butter, vanilla and sugar. Beat in eggs and then add the dry ingredients and mix well.
Turn the dough out onto a floured surface and shape it into a cylinder about 3cm in diameter. Wrap it in baking paper and chill for at least 30 minutes.
Remove from fridge and cut into 5mm think slices. Arrange on the trays and sprinkle the tops with a little raw sugar if you have it. 
Bake for 10 minutes or until they feel firm to touch.

*The key is good dark cocoa, buy the best you can for this.