Start by mixing together 4 eggs and 100g sugar in a mixer bowl for 5 minutes at a high speed until it becomes a sponge. Then add 150g flour and fold it into the sponge mix smoothly. Then spread the mixture on a sheet of baking paper to make a sponge layer. Then bake for 15 minutes at 200`c. To make the mousse, mix the 300ml cream and 150g sugar together in a mixer for 2 minutes until it reaches ribbon stage. 300g white chocolate in a microwave for 1 minute. Then mix the melted white chocolate with the cream mixture. By hand fold in with a whisk the melted white chocolate. Then add 50g crushed hazel nuts to the mixture. Take off the sponge from the baking sheet and put it on another clean baking sheet which has to be a bit larger than the sponge. Put the mouse mixture on one side of the sponge then roll it over together with the baking paper and press tightly. Then put it in the freezer for at least half an hour. Melt another 300g white chocolate and add 50ml of sunflower oil to the mixture, whisk until the oil is folded into the chocolate. Take out the white chocolate roll from the freezer, take off the baking paper and put on another baking sheet. Pour the chocolate over using a tablespoon. Grate white chocolate and sprinkle crushed hazel nuts at the top of the roll