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 centre of the oven for 22-25 minutes, or until a skewer inserted into the centre of the cake comes out clean. Leave the cakes in the tins for 10 minutes then remove and place on a cooling rack. Allow cake to cool completely.
Stir the icing with the salted caramel sauce and spread a quarter of mix over one of the cake.
Place the remaining cake on top and cover the top and sides with the remaining icing mix. Using a palette knife, add texture to the cake by using tip of knife to run grooves around side of cake.
Drizzle the remaining salted caramel sauce over the top over the cake allowing some to drip down the sides of the cake. Sprinkle with some walnuts and serve.Cover and refrigerate the cake for best results.