Preheat a fan assisted oven to 180C/350F/Gas 4.
Lightly oil a 20cm/8in non-stick spring-form tin and line the base with baking paper.
Gently heat the butter and chocolate over a low heat and stir until melted.
Beat together the sugar and eggs until pale and thick, using an electric beater.
Quickly fold the chocolate, almonds and flour into the egg mixture until smooth.
Spoon the mixture into the prepared cake tin and bake in the oven for 50 minutes to one hour, or until just firm.
When cooked, remove the cake from the oven and leave to cool for 20 minutes before removing from the tin.
Meanwhile, place the sweetened espresso coffee into a saucepan, bring to the boil and simmer for a minute until syrupy.
Remove the baking paper from the cake and place it on a serving plate.
Serve the warm cake with a dollop of whipped cream and a trickle of the hot espresso sauce.