Separate the yolk and white of the eggs. Whisk the egg white and salt at first slowly, then at high speed until foamy. Add the remaining ingredients and mix with a spatula from bottom to top. Spread the cake mix on a baking tray lined with greaseproof paper. Bake in a preheated 180 degree oven for 7-8 minutes. After removing from the oven, spread the cake on a kitchen cloth and wrap it. While waiting for the cake to be wrapped, whisk the cream, vanilla and powdered sugar. Add the chopped strawberries into it. Open the cake and spread the cream inside and wrap it. Sprinkle powdered sugar on the roll cake and serve with strawberries.