Separate the eggs, scrape out the vanilla pod, grate the zest of half a lemon, mix approx. 1 tablespoon of cornstarch with a little water.
Slowly heat the milk, egg yolk, sugar and vanilla, add the lemon zest. While stirring vigorously, add the starch until the mixture sets.
Pour into shallow bowls and let cool until lukewarm. Before serving, sprinkle a thick layer of powdered sugar and use a burner (available at a hardware store) to caramelize the sugar until it is nice and brown. Granulated sugar is also possible as an alternative.