To a pan using the double boiling method, add cooking chocolate and milk. Mix well and let the chocolate melt. Slice the chocolate sponge cake horizontally into three layers. Add a slice of lemon in the sugar syrup. Using a brush apply the sugar syrup on both the layers of the sponge cake before adding a layer of melted chocolate truffle. Coat the cake from all the sides with melted chocolate truffle. Transfer the cake to the serving plate. Fill whipped cream in a piping bag and decorate the cake. Garnish with strawberries.