Place the raisins in a small bowl and add 3 tablespoons of rum (or cognac if you don't have rum; or water if you are cooking for children or you don't want to you alcohol).
In a medium bowl, combine the egg yolks, the vanilla paste, half a tablespoon of sugar and a pinch of salt.
Use a hand mixer to mix until creamy.
Add flour and milk, not everything at once, but bit by bit, mixing as you go along.
Continue until you have added in all the flour and milk.
Pour in the melted butter. Don't worry if the batter is rather runny, that's perfectly fine.
Cover the bowl with a kitchen towel or lid and leave to rest for 30 minutes at room temperature.
After that time, use the hand mixer once more to briefly whisk the batter.In another medium-sized bowl, whisk the egg white to stiff peaks.
Slowly and carefully add the whisked egg whites to the main batter until fully incorporated.
Finally, add the strained raisins (i.e. without the liquid) to the batter.
Add the butter to the frying pan.
Once melted, pour in the batter - approximately 1cm high. Depending on the size of your pan, you might have enough for two pan fulls.
Over a medium heat, let that batter brown on one side without disturbing it.
Use a spatula to carefully check the browning process.
Once browned enough, quarter the batter with your spatula and turn the pieces.
Brown these pieces as well, then divide into bite-size pieces with the spatula while still in the pan.
Add a teaspoon of sugar, turn the pieces and briefly leave to caramelise briefly.
Serve with a dusting of icing sugar. If you want to keep it warm, use a baking tray lined with baking paper or a casserole dish and keep warm at 80°C (upper and lower heat is best here; don't use a fan to avoid drying the Kaiserschmarrn out).
If you have enough batter for a second pan-load, give the batter a quick whisk to distribute the raisins which have sunk to the bottom of the bowl and make sure you add more butter to the pan before pouring in the batter.