Preheat your oven to 180°C (160°C for fan assisted ovens) Gas Mark 4. Have ready a greased and lined baking tin.
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 mixture evenly into lined baking tray.
Bake in the centre of the oven for 23-25 minutes or until a rounded knife inserted into the centre of the cupcake comes out clean, then cool on a cooling rack.
Place a damp, clean tea towel on the work surface, then place greaseproof paper on top. Lightly dust this with icing sugar.
Turn the cooked cake out on top of the tea towel and greaseproof paper and carefully remove the tin and the greaseproof lining. While the cake is still warm, carefully begin to roll the cake towards you using the longest edge. Once you have rolled the first edge, hold the tea towel at the other end of your roll and gently pull it towards you - the cake will roll in the paper. Place your rolled cake on a cooling rack and allow to cool completely.
Stir the peanut butter, caster sugar and vanilla essence until well combined and then gradually fold in the chopped chocolate peanuts. Carefully unroll your cake and spread the peanut butter mixture over the surface. Re-roll the cake as before and place on your rack to cool.
Ice the cake with the chocolate frosting and (if you fancy) - your favourite chocolate sweets. Then pop in the fridge until serving...Simply delicious!