For the candied orange peel:

Slice off thin pieces of peel from 1 large orange and cut into thin strips (julienne). Blanch in boiling water a couple of times (to remove the bitterness) and set aside.

Bring to a boil 130g sugar with 130g water. Once the sugar has dissolved remove half the syrup to a bowl and add 40ml Grand Marnier or Cointreau. Set aside. 

Add the orange rind to the remaining syrup and simmer slowly till the rind is glossy and candied. Drain the rind (adding any remaining liquid to the reserve syrup), set aside a few pieces to decorate the cake and chop the rest finely. Set aside.

For the cake batter:

In a mixer beat together 1 egg, 2 yolks and 75g sugar till light and white and mixture forms ribbons when the whisk is lifted out. Sift in 15g cornstarch and 15g cocoa powder and mix delicately. Fold in 60g ground almonds. Set aside.

Whip up 2 egg whites till you see hard peaks forming and then add 20g sugar and beat briefly till the egg whites become glossy. Mix in a couple tablespoons of the meringue into the cake batter to soften it and then fold the remaining egg whites. 

Bake at 200c in a 7-inch round cake tin (line the bottom with parchment paper) for between 25-35 minutes depending on your oven (till a cake tester comes out clean and the cake sponges back to the touch). Remove from the oven and cover with a clean dishcloth. After a few minutes, turn onto a baking grill and let cool completely.

For the icing:

Meanwhile, whip up 3 egg whites till you see hard peaks forming and then add 30g sugar and continue beating till glossy. Set aside.

Melt 100g dark chocolate. Fold in 2 egg yolks and 50g margarine or butter  into the melted chocolate. Fold in the egg whites.

To assemble the cake: 

Flip the cake over if you haven’t already done so (so that the flat bottom is now on top) make a small mark on the edge/side of the cake with a knife (so the cake can be easily re-aligned later),  then cut the cake in half lengthwise and set the top layer aside. 

Dab the inside of the cake with syrup quite generously using a pastry brush. Spread some of the chocolate mousse on top (about 1/3), sprinkle with all the chopped orange peel evenly across the top. Place the top layer of the cake (align it up!), and then dab with the remaining syrup and cover the entire cake with the remaining chocolate mousse. Decorate the sides with chocolate vermicelli or chocolate shavings. Decorate the top with the remaining orange peel

Serves 6-8. You can increase the quantities for a larger cake pan.

The cake can be made and assembled up to 24 hours before serving.