Break 7 oz (200 g/7 oz) of the chocolate into pieces and put in a bowl with the butter.
Melt in the microwave oven for 2 minutes on HIGH Mix well.
Add the cane sugar syrup.
Add the egg yolks one by one to the melted chocolate, beating vigorously with a wooden spoon after each addition.
Beat in the cornstarch (cornflour).
Whisk the egg whites to firm peaks and fold carefully into the mixture.
Put a circle of non-stick parchment (greaseproof paper) in the base of a souffle mold (mould) 7 inches (18 cm) in diameter.
Grease the paper, spoon the chocolate mixture into the mold (mould) and microwave on HIGH for 10 minutes.
Leave the cake to stand for 15 minutes.
Turn out on to a rack and leave to cool completely.
When the cake is cold, cut horizontally into 2 equal layers.
Spread the bottom layer with two-thirds of the apricot preserve and cover with the second layer.
Force the rest of the preserve through a strainer (sieve).
Microwave the puree for 30 seconds.
Coat the top and sides of the cake.
To make the frosting (icing), break the remaining chocolate into pieces and melt with 2 (1) tablespoons of water in the oven for 2 minutes on HIGH.
Mix, add the sour cream (creme fraiche) and mix again.
Pour the frosting (icing) over the cake and spread smoothly with a metal spatula.