Line the baking tray with parchment (see the write up above for details of using different sized tins)
Crush the biscuits
Melt the margarine and pour in the biscuit crumbs, stir well
Very firmly, press the crumbs into the base of the lined tin. Level off and place in the fridge to firm up
Gently melt the Biscoff spread and pour over the chilled biscuit base. Level off and place back in the fridge to set
Melt together the chocolate and 1 tsp margarine. Smooth over the set Biscoff layer and place back in the fridge to set.
Once set cut into three even sized bars