This recipe provides instructions for making a chocolate orange mousse cake. It has five layers: a biscuit base, a chocolate mousse layer, an orange mousse layer, candied orange slices for garnish, and an orange jelly topping. The biscuit base is made by crushing Oreo cookies and mixing with butter. Chocolate and orange mousses are made by beating cream, adding gelatin to juice or melted chocolate, and folding into the beaten cream. Candied orange slices are made by boiling and cooking orange slices in syrup. Orange jelly is made by cooking an orange jelly mix and pouring it over the assembled cake layers in the springform pan.