Strudel with ricotta

Ingredients:
- 500g filo pastry
- 80g butter
- 2 egg yolks
- 50g sugar
- 1 pinch lemon zest
- 2 spoons rum
- 300g ricotta
- 1 spoon cornflour
- 3 egg whites
- 1 pinch salt
- 50g sugar
- 1 egg yolk and a bit of milk to spread

Mix the soft butter until fluffy and add gradually an the egg yolks, sugar, lime zest, rum and vanilla sugar.