Instructions

1. Slice the bread into half cm disks and put them on a plate for a few hours to dry out (preferably overnight).
2. Preheat the oven to 180°C.
3. Mix the icing sugar with the ground poppy seeds and lemon zest (if used). Set aside.
4. Heat the milk - before it reaches boiling point, turn off the heat and add the egg yolks, granulated sugar and vanilla sugar. Stir until you get a smooth, silky sauce. It should not be thick custard!
5. Grease a medium heatproof dish with butter. Spread a little butter on both sides of the bread slices, then place them in the dish tightly next to each other. Spoon over a little milk and using a silicon brush, cover evenly on the bread. Sprinkle with poppy seeds, then add the next layer of buttered bread slices. Brush with milk and scatter some poppy seeds on top.
6. Repeat this process until all the bread is used up. Pour the reaming milk over the top layer and add cover with poppy seeds.
7. Put the dish into the middle of the oven and bake for about 25 minutes or until the top is golden brown.
8. Serve it warm with vanilla custard if you like.