Preheat a fan assisted oven to 180°C.
Lightly oil a 20cm 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 with an electric beater until pale and thick.
Quickly fold the chocolate, almonds, and flour into the egg mixture until smooth.
Spoon the mixture into the prepared cake tin and bake for 50 to 60 minutes until just firm.
Cool the cake for 20 minutes before removing it from the tin.
Simmer the sweetened espresso in a saucepan for one minute until syrupy.
Remove the baking paper and place the cake on a serving plate.
Serve the warm cake with whipped cream and the hot espresso sauce.