Add sultanas and rum to a bowl and allow to soak for 30 minutes. Then drain and allow to dry.
Whisk the egg yolks, sugar and salt until pale yellow and thick with an electric mixer. Stir in milk and vanilla essence. Gradually stir in the flour and sultanas.
Whisk the egg whites until very stiff and fold into the batter.
Heat a tablespoon of butter over a low heat in a deep frypan, about 20cm across.
Pour in half of the batter about 1/2 cm deep. Heat for 4 minutes until the batter has risen and the underside is lightly browned. Remove from the frypan; add another tablespoon of butter to the frypan, flip the pancake and cook the other side for 4 minutes.
Break the finished pancakes with two forks into 6-8 pieces and place on a preheated plate. Do the same with the rest of the batter.
Heat the remaining butter and fry all the pancake pieces again for 2 minutes in the hot butter turning once. Pile on a plate and dust with icing sugar. Serve with compote or jam.