Preheat the oven to 180˚C (160˚C for fan assisted ovens)/ Gas Mark 4.
Mix the eggs, oil, water and cake mix gently together and whisk (by hand or electric mixer) for 2-3 minutes until smooth and creamy.
Pour the cake mixture evenly into the two greased cake tins.
Bake in the oven for 22-25 minutes, or until a skewer inserted into the centre of the cake comes out clean. Leave in the tins for 2-3 minutes then turn out onto the wire rack and leave to cool.
Spread 1/3 of the lemon icing over one of the cakes then top with the strawberry jam. Place the second cake on top and spread the remaining icing over the top and sides of the cake, using the palette knife to give a smooth finish. Chill the cake in the fridge for 30 minutes.
Mix together the cocoa powder and vanilla extract with ½-1 tsp water, to make a smooth, thin chocolate paint. Cover the work surface around the cake with kitchen paper. Lightly dip a new firm-bristled paintbrush into the chocolate paint then gently flick the bristles of the brush with your fingertip all over the top and sides of the cake to give a speckled effect.
To make the nest mix together the shredded wheat and melted chocolate in a small bowl. Spoon into the foil-lined bowl and use the back of a teaspoon to form a nest shape. Chill in the fridge for 1 hour or until set. Gently peel away the foil and sit the nest on the top of the cake. Fill with mini eggs and add a fluffy chick.