Remove the crusts from white bread and crumble finely. Wash and dry lemon and peel carefully with a peeler. Put milk and lemon peel in a saucepan and cook slowly for 4-5 minutes at low heat.
Remove lemon peel. Add butter and 50 g sugar and cook over medium heat, stirring continuously, until butter and sugar have dissolved. Remove the pan from the heat and stir in the bread crumbs.
Allow to cool to room temperature. Separate the eggs, stir the egg yolks into the mixture one after the other. Pour the mixture into a well greased casserole dish (30x20 cm, approx. 1 1/2 litres). Bake in a preheated oven (electric: 175 °C/ gas: level 2) for about 25 minutes.
In the meantime, beat the egg whites until stiff, adding 50 g sugar. Take the pudding out of the oven and let it cool down for 4-5 minutes. Heat 75 g jam until it is liquid. Spread evenly on the pudding.
Spread the beaten egg whites on top in a wavy pattern. Put the pudding back into the oven and continue baking at the same temperature for another 10 minutes until the surface is light brown. In the meantime, heat the remaining jam with 1 teaspoon of sugar and steam the cranberries for 2 minutes.
Let it cool down a little. Decorate the pudding with cranberries and lemon balm.