Bring the milk to the boil, stirring repeatedly with the whisk. Add the xucker, cinnamon and vanilla and stir in the semolina and oat bran. Simmer gently, stirring constantly, until the mixture thickens a little.
Add a piece of butter, the lemon zest and the thick juice, stir well again and serve. Tastes pure or with applesauce, warm or cold.