Cream butter/margarine until light and fluffy. Add egg with a little icing sugar and cocoa, beat well. Gradually add remaining icing sugar and cocoa, beating well after each addition. Add milk gradually, beating until mixture becomes light and fluffy.
Sprinkle gelatine over boiling water in a heatproof bowl, stand over simmering water until gelatine dissolves. Allow to cool completely. Beat cream until soft beaks form and then stir in cold gelatine mixture.
Wash and hull strawberries, reserving a couple of strawberries for decoration. Chop remaining strawberries finely and sprinkle with sugar. Allow to stand for 5 minutes. Drain strawberries and combine the syrup with the cream.
*Put one layer of a cake on the serving plate. Spread evenly with approx. 5T of chocolate cream. Spread 1/2 the strawberries and 1/4 of the cream.
*Put another layer of cake on top and spread with 1/4 of the remaining chocolate cream.
*Top with the 3rd layer of sponge and spread with some chocolate cream, remaining chopped strawberries and cream as for first layer.
*Top with remaining cake. Combine remaining chocolate cream and strawberry cream and spread over the top and sides of the cake.
*Decorate with remaining strawberries.
*Refrigerate.