Begin by making the sable dough, cream the butter and icing sugar together in a bowl until it is light and fluffy.
Place the flour, cocoa powder and ground almonds in a different bowl and stir to mix it together.
Slowly add in the egg until it is fully mixed. Fold in the flour mixture until it is evenly combined, but don't overmix it, or the sable will be tough.
Take a square cake tin that is 20cm x 20cm and line the base with greaseproof paper.
Tip the sable mix into the base of the tin and using a spoon, or rolling pin flatten the dough out so that it fills the pan in an even layer. Prick the mixture all over with a fork and then place it in the fridge to rest for 30 minutes.
Preheat the oven to 180C/170C Fan and bake the sable base for 20 minutes
Whilst the sable is baking, make the florentine topping. Put the butter, caster sugar, liquid glucose and cream in a saucepan and bring to the boil.
Remove the pan from the heat and stir in the almonds and the cacao nibs until they are fully mixed.
When the base has been baking for 20 mins remove it from the oven and spread the florentine topping evenly over the base.
increase the oven temperature to 200C/190C Fan and bake for a further 10 mins until just starting to golden. Remove from the oven and leave to cool slightly.
After about 10 mins leave the florentine sable in the pan, but using a straight edged knife slice into 16 and then leave in the pan until cool to touch. If you let it cool too much before cutting, it will become brittle - so you need to cut it while it is still warm.